"Forced into a duel of wizards at the mysterious Rainbow Castle, you are magically separated from your teacher and grandfather, Pentegarn, who battles for his life against three evil wizards. You must get back to him!" --from the back cover
Revenge of the Rainbow Dragons, by Rose Estes, is unique in that it's the only non-licensed Endless Quest book that is a sequel to an earlier book (to my knowledge, anyway--I never read most of the later 'first series' nor any of the 'second series' EQ books). The characters of Jamie, Fox, Owl, and Pentegarn return from Pillars of Pentegarn in this book. Baltek the Fighter and Lydia the Thief do not return (maybe the official ending was one in which they died? It doesn't say...)
Jamie, the protagonist, is now a teenager, and an apprentice wizard. You've got only a few spells, but Pentegarn's blood gives you an innate ability with magic, so you've got a lot of potential (in other words, don't expect Ms. Estes to stick to the Vancian rules of D&D...although there was at least one place where she mentioned having to 'refresh' spells). However, before your training is complete, word that Pentegarn is back in the Pillars reaches three evil wizards, Malus, Pothos and (I keep wanting to say Aramis) Rubus. These three have claimed magical rulership over the district, and challenge Pentegarn to come to Rainbow Castle and duel with them.
The book starts out in a way that made me leery, despite remembering that as a kid I enjoyed this book. The first choice is a non-choice. Pick the wrong one and it sends you to the other choice anyway. The second choice is the same. Again, I get the feeling they were thrown in as a way to break up the overlong introduction. But the third choice is where the real adventure begins, and it gives you three options that lead to three different adventure locations.
Basically, the three wizards want you out of the way while they duel so you don't cheat for Pentegarn (and they can cheat against him, of course). So they offer to send you to Limbo, the Game Room, or the Tower. The Tower course is the most limited, as it has a few options that send you to Limbo or the Game Room, but can lead to its own good ending. The Game Room option again has a way to lead to Limbo, and has two good endings that you can find. The Limbo option also has two good endings. Bad endings in this book pretty much mean death (or permanent magical transformation). There's only one neutral ending I remember where you escape with Owl, leaving Pentegarn and Fox to their fates.
There are some fairly interesting things to encounter in the book, and some nice, unusual locations. It doesn't read like a typical D&D adventure, but it doesn't feel 'wrong' either. One oddity is that there is a place where you can meet a guardian who has some magical colored stones that you need to arrange to escape. The book actually has a half page illustration, and suggests cutting them out or tracing them to actually do the puzzle yourself. The opposite page is an illustration, so you wouldn't lose any text if you did cut them out, but I wouldn't want to. When I was a kid, I'd checked this book out from the library so of course I couldn't (I remember I did trace them, though, and did the puzzle).
The rainbow dragons are a bit weak, actually. There aren't that many ways you can encounter them, and they breathe rainbows as a breath weapon. That may be the reason the three bumbling evil wizards were able to oust the dragons from Rainbow Castle. But despite that, the book is entertaining. It's not quite as good as Pillars of Pentegarn, but then I think that's one of the top books in the series.
The art is pretty good in this book. The cover is a rare Easley painting rather than an Elmore. The interiors are by Harry J. Quinn, who did Pillars of Pentegarn, so there's a feeling of continuity with the art.
Overall, I enjoyed this book. It has a few flaws, but it's got a lot of good ideas, and some non-standard situations that break some D&D tropes in a good way. It has a variety of paths that lead to good endings despite the linear beginning.
Protagonist: Apprentice Wizard, much improved over his first appearance
Sidekicks: The bickering Fox and Owl return for more of the same
Adventure: Interesting. Not quite D&D, but varied and strange.
Endings: Quite a few good endings, mostly deadly bad endings.
Art: Nice cover (Easley), cool interiors (Quinn)