"If you liked this book..."

Amazon has a feature that uses your purchase record to try (sometimes with odd results) to predict what other books you might like. They're trying to sell more books, of course, but they give it a polite and helpful feel; and sometimes it is helpful. But there's no substitute for exploring in a library or used book shop, and lighting on the book you never guessed you'd like or the subject you didn't realize you needed to know. I'm still discovering the world, and still discovering me.