Books like Synthetic Men of Mars

Edgar Rice Burroughs had this problem in all of his series: After a while, the quality of the books would start to slip -- maybe he was getting bored or maybe he'd just start repeating himself. Arguably, this is where the Mars series begins its downhill slide (which means that, percentage-wise, John Carter has less dross than the other major series -- Tarzan, Venus and Pellucidar).This book is again narrated from the perspective of a native Barsoomian, Vor Daj, who accompanies John Carter on one of his adventures. Carter plays a fairly minor role in the book, really, and is off-stage for much of it; otherwise he'd probably overshadow Vor Daj. Ras Thavas, the Master Mind of Mars also returns, so this book again has some science fictional elements -- brain transplants and artificial life and the like. Naturally there's a beautiful woman; naturally Our Hero falls for her; naturally, the Fates conspire to make things as difficult as possible for them until the end.This isn't so much an actively bad book as it is somewhat tired and occasionally silly. I wouldn't say it should be avoided, but I wouldn't say it needs to be sought out unless you absolutely, positively have to read more Barsoomian adventures. (For which I wouldn't blame you -- I've certainly read the book many times over the years.)