Introduction to Search with Sphinx by Andrew Aksyonoff, O’Reilly Media 2011. About 146 pages. (Here’s a link to the publisher’s page.)
This is an engaging short introduction to Sphinx. At 146 pages, you shouldn’t expect it to go into every detail, and it doesn’t. There are major topics that it omits entirely or mentions only tangentially, such as distributed searching across a cluster of machines, real-time updating of indexes and attributes, and so on. But although the book doesn’t boil the ocean, it does a great job at covering an introductory subset of Sphinx. It’s just the book you need to get rid of MyISAM full-text indexes and return MySQL to proper performance again.
This book is about how to get started with Sphinx: getting it up and running, basic configuration, creating and maintaining indexes, and querying with the SphinxAPI and SphinxQL languages. It covers relevance and ranking, so you can understand how Sphinx is different from most relevance engines and why it produces better results.
If you haven’t explored Sphinx, you should start with this book. If you know Sphinx, it might be redundant to you.
Either way, it’s a fun book to read. Andrew is a great writer with a charming sense of geeky humor, and he makes a lot of jokes in his examples. These don’t interfere with the learning, but they do make it a lot less dull. (It isn’t forced or overdone, either, unlike a lot of books that have to make constant Beatles references at every opportunity.)