There is a really interesting article at publishersweekly.com. Just search for Nancy Pearl for the interview with her at the latest Public Library Association meeting.
She believes that "reading is about experiencing joy". Her definition of a good book is "one that I enjoy, just as a good book for you is one that you enjoy. We may agree, or we may not, on what’s a good book;...the only opinion that should matter is our own."
She has an interesting idea about how to recommend a good book. Nancy says "We often start by matching the book a reader has just read with other books on the same general topic or in the same genre. But when we link books by what they’re about—primarily, the plot details—I think we misunderstand what really goes on in our reading lives. When we want a book exactly like the one we just finished reading, what we really want is to recreate that pleasurable experience. We need to start thinking about what it is about a book that draws us in, rather than what the book is about."
Nancy says there are "four experiential elements: story, character, setting, and language". She calls these “doorways,” and says we should choose our next book by asking ourselves in what proportion we want these elements in our next book. For example, "a book with story as its biggest doorway is one that readers describe as a page-turner, a book that they can’t put down because they desperately want to discover what happens next. A book with character as its biggest doorway is a book in which readers feel so connected with the characters that when the book is over they feel they've lost someone dear to them. Readers of novels in which setting is most prominent say things like “I felt like I was there". A book in which language is the major doorway leads readers to utter sentences like “I read more slowly because I wanted to savor the language” or “I’m not even sure what the book is about, but I loved the way the author wrote.”
The trick in finding your next good book is to find the proportion of story, character, setting, and language that closely matches a book you loved. This idea is actually quite logical. I'm going to try it the next time I'm asked to recommend a book.