Worth reading for Herovitt's World alone...
I bought this recently because it includes the short novel, "Herovitt's World"(1973), which is a neglected classic-basically, it's a devastatingly funny portrait of a hack SF writer, who's on the verge of a psychological collapse. I read that book about a decade ago, and I'm glad to say that it holds up upon re-reading.
The other stories in "Passage of the Light" are also quite good albeit not as great. (Basically, this is an anthology of Malzberg's stories which are about SF and or SF writing.) If you only know Malzberg from such depressing and bewildering novels like "Beyond Apollo", then give this a try, since all of the stories are highly entertaining and funny and sometimes even brillant. The only downside of this collection is that it doesn't include "Galaxies", which is probably Malzberg's best novel after H.W. (although it does include the short story which was the basis for G...)