The only valid response to being asked to do reader's advisory.

Readers' advisory sucks. Books are such a personal thing. It's actually one of the hardest parts of my job. Luckily there are many tools available to patrons to help them discover new books.

• Always ask your library staff. I may not like doing reader’s advisory but I realize how important it can be to patrons.
• NoveList, which is a database probably available through your library, lets you get similar reads by author, title, series, narrator, and keyword.
• Fantastic Fiction offers a "Similar books by other authors" section at the bottom of each book page and a "Visitors to this page also looked at these authors” section at the bottom of each author's page.
• LibraryThing offers a "LibraryThing Recommendations" section on book pages. There are also tag clouds for books and authors.
• Literature-Map allows you to put in an author's name and get similar authors in return, and the effect they use is pretty nifty...like a constellation of authors.
• Whichbook offers searches by mood and emotion, world map, character and plot, and bestsellers.
• Goodreads offers a "Lists With This Book" section on book pages.