In talking with other Barbara Hambly fans, the Sun-Cross novels rarely come up. Why? I am not really sure.
Certainly they are much darker in tone, compared to her other fantasy novels, which are not, themselves, particularly frothy or cheerful. Her characteristic ascerbic comments and throwaway, casual references to horrors are even more to the fore here.
The world-setting is a characteristically Hambly one: wizards are a presecuted minority, the Church is corrupt and bigoted; the settings may be fantasy, but the portrayal of human nature, often at its worst, is thoughtful and realistic. This background description could equally fit the Darkover novels or the Windrose Chronicles, but whereas in those novels, the background serves as the setting for heroic actions against an alien foe, and a love story, in "The Rainbow Abyss" the social setting comes to the fore and becomes the driving point of the plot.
Probably this review will drive some people away, but for those who like their fantasy thoughtful, unflinching and memorable, this is heartily recommended. It is the sort of story that you do not just read avidly, you then find yourself discussing it long afterwards.
I am reluctant to give the plot away, over than to say that it primarily about a student's devotion to his master, the wizard Jaldis, who has been tortured and crippled by hostile politicians. Working together, they hope to escape to another world, where magicians are welcomed and appreciated.
Why only 4 stars? Some elements of the setting are rather clicheed, and she reiterates familar themes of hostility to organised religion.
The sequel, "The Magician's of Night" suffers from none of the above flaws. It is original, brilliant, and justifies the harshness of the imagery used in this book. But it works best as a sequel, with the back story of the main protagonist clearly examined in "The Rainbow Abyss" - so, do give a chance to the quiet hero here!