They're all available for Kindle, of course, but they're all $14.99 apiece. I'm not saying they're not worth it, merely that you might prefer to wait for a sale. Because, yes, e-books do go on sale -- the challenge is finding out when that happens.
Savvy Amazon shoppers know about price-tracking service CamelCamelCamel, which can alert you when prices drop. Sadly, it doesn't support Kindle titles. For that you need a different service: eReaderIQ. It not only catalogs Kindle books that are free and on sale, but also lets you create alerts for tracking specific books.
Before I explain how to set one up, let me first note that although eReaderIQ is free, it relies on donations. If you find the service valuable -- meaning it routinely saves you money on book purchases -- consider supporting it with a percentage of those savings. The developer previously relied on Amazon's referral program, but that's no longer working out. This is a little guy trying to make a buck while helping readers save many bucks. Support him!
Step 1: Head to eReaderIQ and sign up for an account.
Step 2: Click Track Books, then Track Price Drops.
Choose one of the four available tracking options. For example, if you already have the Amazon book listing open in another tab, copy that URL and then click the Add by URL option. And if you've already added some titles to your Amazon wish list, use eReaderIQ's import tool to start tracking them.
Step 4: Click the Track It button for the selected book, then modify the "drops by" price if you like. For example, if you don't want an alert unless the price drops at least $2, enter that amount in place of the default $0.01.
The site also offers some integration tools, including bookmarklets (1-Click Watcher) for quickly adding any Kindle title to your watch list and a Chrome extension that also lets you check price histories and watch non-Kindle books so you can get notified if they become available.
For anyone who loves Kindle books and is serious about saving money, eReaderIQ is an invaluable tool.