I'm not aware of many books being published for some other type of BASIC on the Amiga, though.
FYI: There were gazillions of books published about True BASIC back in the 80s and 90s. There are more books about True BASIC than all other versions of BASIC for Amiga put together. Dozens of different books.
And there are lots more books about algorithms which are not about True BASIC per se, but they include True BASIC source code on the accompanying floppy disk. Lots of different science books and algorithm books used that technique so they could support multiple langauges in a single book.
The thing is that True BASIC is a multiplatform language. It is the same language on Amiga, Atari ST, Mac, Windoze and Unix. This is why there were so many books written about it.
It has most of the advantages of JAVA, without all the horrible disadvantages of JAVA, 10 years before JAVA ever even existed. It has write once, run anywhere technology built-in for free. You can compile your programs into byte-code and distribute the byte-code versions. Or you can distribute the source code. Whichever.