It's not as easy to find good books on tube electronics anymore, in this age of the semi-conductor. But tubes have their own fascination and features that make them unique, which starts with the fact that tubes are basically voltage-controlled devices and transistors are basically current-controlled devices.
This book contains a fun collection of DIY projects aimed mainly at those interested in building their own OTL (output transformerless amps). But there are several other projects as well, such as a tube tester and a low power amp that are also interesting in their own right. There's tons of miscellaneous useful information on various tube concepts that will expand your knowledge. The book starts out with a basic introduction to electronics and tubes that even an inexperienced non-hobbyist and non-engineer would be able to follow with a little effort.
If you want a general introduction to tubes that includes more specialized tube concepts such as lighthouse tubes (a type of triode tube useful in ultra-high frequency applications such as microwave communications), cavity resonators and cavity magnetrons, tube waveguides, or klystron tubes (also useful in microwave ovens and particle accelerators), you'll need to get a text on general communications electronics such as the classic book by Robert Shrader. But for a terrific little hobby book with some great projects and easy to understand explanations you won't find better than this book.