Harlan Ellison is known first as a short-story writer, second as an essayist, third as a screen scenarist, fourth as a pain in the ... well, suffice it to say that novels are far from the principal format in which he works.
In fact, of the 14 titles listed here, only two are full-length novels of which Ellison was sole author. One is a collaborative effort in which another writer adapted Ellison's screenplay; most of the rest are essentially longish short stories published either in the "double novel" format or alone as chapbooks. The "Harlan Ellison Discovery Series" was his mid-'70s attempt to do for the speculative fiction novel what Dangerous Visions had done for the genre's short story -- with mixed results.