I always recommend Dan Jones' "The Plantagenets" as a starter book bc it covers the basic facts pretty well, is an easy intro, and is up to date with the modern research. It also gives more of the background to their dynamic so you can understand why each of their reigns was the way it was.

For more advanced stuff, I'm currently reading Sir Maurice Powicke's "The Loss of Normandy" which is more detailed regarding the later years of Richard's reign and the beginning of John's, with a heavy emphasis on the warfare and conflicts between the Angevins and Philip Augustus. I like it a lot, though it's more academic and also you'll really need a map of Normandy to follow along lol.

For Richard specifically, I enjoyed Jean Flori 's and John Gillingham's biographies of him a lot; both are very good historians who disagree on some subjects, but I think whose work makes up pretty much the authorities on the subject. I'm not as versed in John-specific biographies I'm afraid (blorbo bias...)

I really feel like the kind of "Good vs Bad King" lens thru which both figures are viewed from is pretty reductive. Since they kind of emerge from very different contexts and had to deal with similar but different issues in rule, and of course are connected. I think understanding Richard and his decisions and where he left off at his death kind of helps in understanding John and his deal as well, and of course the relationship and conflict with Philip overall in the contentious king-duke-vassal relationship I think is the key to understanding the dynamics overall.