The Ghost Update has changed the way the Book of Life functions a bit. Now, instead of bringing dead Sims back to life, the Book will summon the Sim's ghost to the current lot as a visitor. The Ghost arrives regardless of time or place (I was able to summon a ghost to the Park at 7 am.) The Ghost arrives as a normal visitor would (appearing in the street), unless their Tombstone/Urn is near, in this case the ghost appears next to it. The only exception I encountered was an Urn on an end table, the ghost arrived as a normal visitor rather then appearing near the urn. Unlike before, when Summoning a Sim brought them back to life and consumed the book, summoning a dead Sim does not consume the book, allowing it to be re-used to summon the dead Sim at will. But having the Sim available at will makes adding them to your household and bringing them back with Ambrosia much more easy.
The summoned ghost seems to stay for a while, on my home lot I summoned three ghosts at 11 am and they all started to leave at 9 pm. However, in the case of the urn on the coffee table the ghost appeared unable to leave the lot, she just hovered in place complaining (peeing on herself and such). When I moved the urn onto the ground the ghost immediately headed over and dissolved as normal, no doubt a bug/routing issue.
If you click on a Sim's tombstone/urn and select "Realse Spirit to Neatherworld" the Book of Life is no longer able to summon that Sim's ghost. The Sim appears to still exisit in the game as their Tombstone/urn still displays their name, they're still in the relationship panel, and you still get an option to "Read [Sim]'s Epic Tale" from the Book of Life. Until another method to bring a dead Sim arrives in-game this seems to be irreversible.
Finally, since dead Sims now appear like normal Sims (other than being Ghosts) in the relationship panel instead of being sorted to the bottom and greyed out, I wanted to see if you could bind a Book of Life to a Ghost. Alas, dead is dead and even Ghost Sims cannot be Bound to a book it seems, I even tried inviting a ghost into my household and they still could not have their tale captured in the book. So the rule of only capturing the tale of a living Sim is still in place. Oddly enough, I was able to bind the Grim Reaper to a Book of Life but this had no additional features. I wasn't able to Summon Grim, only "Read his Epic Tale." For all I know, capturing Grim's tale in the Book of Life was available pre-patch and I just never noticed it.