Anyone know a good book to address the denial, pain, and shock family members feel as they watch their loved ones decline from dementia?

Memoir by Eleanor Cooney, Death in Slow Motion.
Memoir by Elizabeth Berg, I'll Be Seeing You.
Under fiction, story about a man's descent into alzheimer's from his perspective by Author who spent years volunteering in ECF. That one is Still Time by Jean Hegland.

I seem to be a little late in offering suggestions for you, but here are some anyway. First, are you looking for a book that your dad can read? I don't believe there are any that a person living with dementia could understand or retain, unless they are in the very early stages. However, there are a lot of informative books, videos, and websites available to help you, the caregiver, weather the storm of being a dementia caregiver. The very best book I've read is “Surviving Alzheimer's” by Paula Spencer Scott. Although Alzheimer's is in the title, it addresses issues common to all dementias and caregiver concerns. It discusses stress, guilt, grief, dementia behaviors, why they happen and how to cope. Another excellent book is “Learning to Speak Alzheimer's” by Joanne Coste. It too, deals with more than AD. For an easier read, you might want to look at “Hope for the Caregiver” by Peter Rosenberger. Others have cited “The 36 Hour Day”. Knowledge is Power so educate yourself about your father's and your journey thru VaD. You'll need more than a “quick read” to be able to cope with the challenges of caregiving.

I just bought the 36 hour day that a friend recommended.

The Hospice Psychologist can help you.

Would he be better off in a MC unit? My mother's facility was IL/AL/MC, but she moved from condo to MC, skipping the other levels as she needed the locked down area. It is never a good idea to lock MC residents in their rooms (many tend to walk a lot and can really resist restraints), so the unit access is a bit more stringent to keep the virus out. The AL and IL residents have been restricted to their own little apartments, but not the MC area. Restrictions meant less outside "activities" could be brought in, for all levels, but regular staff would take up the slack, to keep residents more active and engaged, when possible. Meals were a little more staggered, with tables further apart, otherwise they really didn't change much of the routine. This is important for those with dementia.

As for the siblings, the more they can learn, the better. Online is where I learned most everything (I knew nothing about dementia before that.) I can't really say which sites were better, it was many years ago, and cumulative over several years, but many online site discuss what you might experience and some offer suggestions for how to work around it or deal with it. Distractions. Redirection of focus. Living in "their" moments. Discussing your own "current" events won't likely hold their interest, so you have to dig into their past, respond to what they say, etc.

Some families learn to cope, others don't. I learned quickly to "go with the flow" and "live in the moment." You mention he's worse mornings and evenings, so if you can have them make contact when he's in his "better" times, that might help. Staff might be able to identify the best times for contact.

Both my brothers had their own kind of denials going on. Neither took me seriously when I brought up that our mother was heading down the dementia path. Months later, OB asks what's wrong with mom? If I sent links to help him understand, he would just read the title and say she doesn't have a sleep problem (the title mentioned sleep disorders, but if you read the article, it would help explain her odd OCD behavior she developed before we moved her - we had cameras, and could see this become a nightly marathon, checking various things over and over.) READ IT. I have no idea whether he did or not. During his last trip to the area, we visited once just after he arrived and mom was overjoyed to see him. I sent him up in the morning, suggested he pick up DD coffee and doughnuts. Very short visit. He was here to help clear out the condo, so in a quiet moment, I suggested he go visit her again. He flat out refused, and said he "didn't know what to do with her." Just BE there. So what if she repeats herself. Sometimes you can "dislodge" the stuck moment and move them on to something else. If they get agitated, try to divert attention to something else (not always possible, esp over the phone.) He would NOT go back, because he just couldn't figure out how to be "in the moment." The other would respond with long drawn out answers or explanations, only to have her ask again or make the same statements. Keep it SIMPLE! He was also adamant she needed AL, not MC. Staff said nope.

Ask about something from their past, something that was pleasant for them. Old friends or relatives. Places they maybe traveled to. Funny stories when you were kids. Don't ask if they remember something, just try a topic and if he can't grasp it, move on. Try anything and everything, and stick with those that work to keep them calm, happy, not agitated. If he's stuck in that agitation, perhaps try again later or perhaps he needs Rx (not a fan, but some help.)

I really would consider asking about MC. He might be very unhappy being "stuck" in his room(s). Not all places are the same, but mom's place did allow the MC residents freedom of movement. I would suspect if someone tested positive, they would have to isolate that person, but allow the others their "freedom."

Ask family also to watch Teepa Snow's films on youtube.

I strongly recommend subscribing to the blog of Dr. Leslie Kernisan at https://betterhealthwhileaging.net/ for anyone going through dealing with caregiving for older loved ones. She has a wealth of information there.

A good book by lay person is Elizabeth Berg's book about the decline of her parents and her siblings trying to deal with their move from family home to care. Called "I'll be Seeing You". Another fiction book that looks at dementia from the mind of a man sinking into it is Jean Hegland's Still Time, about a professor just entering in care at ALF. Another memoir is Death in Slow Motion by Eleanor Cooney. These latter two are cheap on Amazon as older. I especially loved the latter. As far as non fiction other than memoir I have no good recommends and if you find some sure would appreciate your posting. Online information and Facebook Groups with people dealing with dementia are very helpful as are support groups, and indeed this Forum.

The 36 Hour Day explains it all - but will they read it?

I think if they're really interested they will already have Googled it, or youTubed it - the internet has it all.

See if you can pick up a few pamphlets from the AL facility your Dad is in. Try the Department of Aging, AARP or the Alzheimers Association.

Have them sign into this site, it's a wealth of information, easy to navigate and even this forum is wonderful.

It has been my experience that people who want to learn will seek out resources to learn, be it books, on line or contact with organizations like the Alzheimer's society. If your brothers are anything like those in my family who are not proactive they probably wouldn't read anything you send them, no matter how simple.

Teepa Snow IS an amazing resource, I particularly liked this video series

https://www.youtube.com/playlist?list=PLVl8vTLjje8ESAEvpjVoVTEK-_6X2jTdl

A lot of people recommend Roz Chast's book "Can't We Talk About Something More Pleasant"

I don't know about any books that are a quick read(although I'm sure there are some,) but I would recommend your family members watch any of Teepa Snow's videos on dementia and all it entails. They will learn much more from the videos than any book. You can find them on Youtube.