I'll admit that I prefer iPhoto's calendars to its hardcover books, simply because if I spend the time creating a calendar, I'm certain it will be displayed (on our wall, or by whomever I give it to) for an entire year. In contrast, lovely as iPhoto's hardcover books are, my experience is that they're looked at a few times and then put away on a shelf. That's not a bad thing - a book may be perfect for documenting a special trip or event and not require constant attention.
But honestly, the other problem I have with books is that they're quite a bit of work to create, at least if you're as obsessive as I am about getting things just right. Even after selecting all the photos and figuring out what, if anything, I want to say about them, iPhoto offers oodles of themes and layout options within each theme. Sometimes I become overwhelmed just picking my desired layout and have to go read email or something easy.
If you're thinking about making a book in iPhoto, my fellow Peachpit author Liz Castro has created a wonderfully useful Web site where she obsessively documents each and every iPhoto book theme. For each theme, she uses screenshots from iPhoto to summarize the outside layouts, the inside layouts, and possible backgrounds.
Then she moves on to provide examples for each layout option, for the cover, for the introduction page, and for pages containing each of the possible number of photos for that theme. Each page is exhaustive, but it's far easier to scan them than to work your way through all the options in iPhoto itself.
Liz first started this site to document the themes in earlier versions of iPhoto, and while the pages for iPhoto '08 are still available, she has updated them all for iPhoto '09. For the most part, the book-related changes in iPhoto '09 revolve around the Travel theme, but it's worth noting that you can add either an introduction page (really just a text page, since it can go anywhere in a book) or a map page to any of the themes, although the Travel theme offers the most customization options. Liz also provides some useful tips on using the new map pages.
So if you're a bit overwhelmed by all the options in iPhoto, or are just looking to figure out what has changed with books in iPhoto '09, drop by Liz's site.