I don’t like them and don’t want to see them. Or, as Dr. Seuss might write: I do not like them here or there; I do not like them anywhere.
Loglines, most often seen in movie advertising, are single sentences meant to capture the plot and spirit of a book (or movie, or TV show). So a logline for something like Harry Potter might be “At age eleven, Harry Potter begins his education as a wizard, and he must fight the evil man who killed his parents.” With a logline, a writer can answer the question, “What is your book about?”
Loglines are harmless in and of themselves, I guess, but for what I have to do as an agent, they’re useless. Agents don’t sign clients based on one-sentence pitches. A book that might have a great hook could fall apart in the writing. The aspect that the writer chooses to pitch in the logline might not be the thing I like best about the book. My usual response to a logline, when I hear one during a pitch, is, “And then what happens?” A logline only tells me one tiny detail about a book. A logline cannot build a world or show a great voice or give details as to how the characters work out their problems.
I’ve been to pitch sessions where writers are required to give them to agents, and while I’m not offended by this, I do question whether is a good use of the writers’ time. Loglines can be useful and/or fun on a book that’s already published. One I really love is the logline used on the advertising for Season 5 of True Blood: Bleed the Fifth. It’s a clever play on words for an already-established TV show. It’s fun because it means something to the show’s viewers, but it doesn’t try to accomplish what I feel that a logline ultimately cannot do: Get me to want more. For a book from a new author I’m looking to sign, I don’t want a logline. I want a fabulous query and killer writing.