"If you like this then you'll love that..." recommendations can be tricky. After all, just because I once bought a frypan from them, Amazon.com seems to feel I am simply pining away for lack of golf tees for the game I don't play, diapers for the baby I don't have, a buzzsaw for the workshop I'd be an active menace in, and back hair trimmers for... sigh
OK, an admittedly extreme example. But a real life one; Amazon has actually explained (admitted?) to me that its recommendations use a marketing algorithm which says that if someone else bought something I did and bought a lot of unrelated stuff as well, then I must want all the unrelated stuff too. The problem is, most you like this / you must try that book recommendations aren't much better, because they tend to rely on relatively superficial stuff like setting or profession or basic genre labels. Sorry, but just because I love Jo Dereske's series featuring librarian Helma Zukas, that doesn't mean I'll love every series featuring a librarian. Any more than my liking Suzanne Arruda's series set in 1920s Africa means that all I need is a lion and an elephant or two and I'm good.
The most effective recommendations tend to be those based on the core of any book: the writing. Not just if it's well written—some people genuinely prefer reliable hack work or simple mind candy, and recommendations for them should take that into account—but the essential style. That usually starts with how thoroughly boiled it is, but should also factor in such things as this writer being a master of characterization while that one (writing superficially similar stories) has characters only because someone has to act out the intricate plotting he really cares about. Or the wry and dry voice of this humorous mystery writer vs. that one's easy guffaws you can see coming a chapter away. The meticulously crafted sentences of this writer vs. the impressionistic style of that one. The way that this writer brings, say, Greece to life as vividly as the unique light that shines on it, while that one clearly believes in just letting his fingers do the walking, with Frommor's and Fodor's as their guide. Greece is an especial bugaboo for me because it's one of my favorite places to visit in real life, a particularly vivid and unique place, but one whose uniqueness fiction rarely does justice to. One recent exception was Jeffrey Siger's newish series, which definitely offers a local perspective rather than one straight from the travel guides.
Now if I could only get amazon to realize that sometimes a frypan is just a frypan, not a gateway to nose hair clippers (do I even want to know what other places they feel I need to be clipped?) and well meant fellow readers to understand that just because Monica Ferris's needlecraft series and William Kent Kreuger's Cork O'Conner series are both set in Minnesota, that doesn't mean fans of one are going to automatically adore the other.
