Here is an obituary. He was arguably the very finest of the 20th century print makers at creating textures. Here is one amazing example of his work; even on the internet the talent is evident. Here is a Terry Winters print with him. Here is a simple Braque print done with Crommelynck. Jasper Johns also did fine work with Crommelynck, whose talents he stood in awe of. Jim Dine benefited greatly from his collaboration; here is Dine's sculptural tribute to Crommelynck. Crommelynck printed this Picasso etching, as well as doing many other fine Picasso works. The talents of print makers are very often underappreciated.
If you are curious as to my (generally positive) views on John Updike, see these previous MR posts.