I picked up this book because I wanted to learn a little more about what is involved in reader's advisory services, and found it to be really fascinating. It's not so much about the service as it is about what makes readers want to read some books and not others. Keeping this in mind, Saricks lays out definitions of genres from a librarian's point of view.
It went slowly trying to read the whole thing all the way through in order to learn about all the different genres, so I ended up skimming the second half of the book. I found it especially useful, though, that Saricks breaks up the genres into groups based on what makes them tick--Adrenaline or Emotion? Intellect (mind-engaging) or Landscape (setting-driven)? The section on Adrenaline genres particularly taught me something as before I'd never heard a clear definition of the differences between Adventure, Suspense, and Thrillers. Now I have a better idea of how those are defined.
The author also points out that genre characteristics cross over into one another, perhaps now more than ever. So, genres don't necessarily have to exclude elements from other genres--they can still be defined as long as there seems to be a main focus (i.e. adventure novels may have romance in them, but the romance is not the focus of the story).
All in all, a very useful reference that I may return to someday. I would recommend it for studying one specific genre at a time rather than trying to take in the whole broad overview.