Roger Zelazny's The Changeling is 40,000 words of very pretty trade paperback,… and I rather wish there had been a few more words. Perhaps there were; there appear to be places where segments that ought to have occurred are simply missing, rather than skimped….

But the author triumphs over the editing (?)…. This is very good science fantasy, counterpointing the lives of two attractive male heroes who, as babies, were exchanged between a magical milieu and our mundane one. (p. 43)

[The] two young men do come into contention—partly because both of them are involved with a particular girl, partly because Mark is such a rockhead—and the old struggle between technology and magic undergoes another climactic cycle.

As noted, this is not a perfectly told story, because of its discontinuities. But it's very good reading when there's something there to read, and filling in your own blanks can be...