Agreed. 3 is fantastic! How can you not own the book with Agrajag in it?
I also prefer the first two radio shows over the books. The remaining radio dramas that adapt books 3-5 (and attempt to reconcile the continuity issues caused by using book 3 as a sequel to radio show 2) are decent, but obviously suffer from many of the same issues that books 4 and 5 suffer from.
Now that I think about it, I've never watched the entirety of the BBC TV series ... I should get on that ...