God bless Amazon: it's now listing books in series.
I've no idea whether this has rolled out completely, but it's wonderful.
Just above the "Also Bought" slider, there's another one: "Books in This Series."
Of course, Amazon may just be testing this. I hope they keep it. Not only is it wonderful promotion for series authors, it's also great for readers.
Sometimes it's a huge effort to find other titles in a series. Yesterday I was checking out a mystery series, and landed on title 18. It was a hassle to find the rest of the titles. The author's website didn't offer much, and you couldn't tell from some of the titles which number they were.
Happy days. Fingers crossed that Amazon rolls this out widely and keeps it.