IF YOU POLLED AUTHORS, you'd learn that "How long did it take you to write this?" comes in ahead of the oft-asked, "Is it autobiographical?" This is because readers expect books to have been brought forth in travail. In the reader's mind, a book that took a long time to write is somehow better than one that didn't. This is one reason a prolific author might wish to resort to a pseudonym.

Not so Lawrence Block. He hasn't bothered faking anything about his output, and thus is often accused of being "slick." What's wrong with slick? Sure beats me. I'd much rather read a lot of books by someone who can write than one by someone who can't.

But maybe an element of jealousy comes unwittingly into play when considering Block's lengthy list of prior credits: Nine books that he lists as novels, 16 mysteries, and three nonfiction works (not to mention that the flap photo, if at all recent, shows a man not nearly old enough for all of this). And now, he's virtually coming out with two books at a crack!

The first of these two is a Bernie Rhodenbarr entry, the fifth in a series of charmingly titled books (Burglars Can't Be Choosers; The Burglar in the Closet; The Burglar Who Studied Spinoza; The Burglar Who Liked to Quote Kipling). Block's Bernie, of course, is the affable thief in the title role.

In 1977, when Block introduced Bernie, the latter hadn't any friends. In the course of that first book, however, Bernie tied up with some folks who figure at least as walk-ons in the subsequent burglar accounts. There's Ray Kirschmann, who is, literally, the best cop Bernie's money can buy. And Mrs. Hesch, a neighbor who wholeheartedly approves of Bernie's selection of prey. There's Bernie's best friend, Carolyn Kaiser, whom he met a couple of books back. And Denise Raphaelson, a single parent whom Bernie, then Carolyn, dated (They're all Just Good Friends now). But it's this continuity and camaraderie, I suspect, that accounts for much of the series' popularity: readers feel as if they're catching up on the progress of very well-drawn characters whom they've come to think of as chums.

Here, as in the earlier Rhodenbarr books, there's a standard issue plot, e.g., Bernie is performing a simple bit of burglary when, voila! he's not just at a murder scene, but indeed he seems the likeliest person to have committed same. The plot in all of the books about Bernie centers on his attempt to extricate himself by finding the guilty party.

This may sound terribly predictable, and it is, in a way. The thing is, readers won't mind unless they're attempting all of the burglar books at one sitting. This is because we aren't reading these for their plot. Oh, granted, if something were amiss with the plot, we'd squawk, but nothing ever is.

It's the snappy patter that moves Block's burglar books along. Really, his characters, and especially Bernie, make wonderful wisecracks. For instance, while burgling, Bernie gets hungry. "I thought of checking the fridge . . . But Sing Sing and Attica are overflowing with chaps who stopped for a sandwich." Caught red-handed in an apartment where he's hoped to steal a Mondrian, Bernie tells the cops, "I just wanted to look at it. The museums all close around six and I had a sudden urge to bask in the inner glow of great art." Later on, when Bernie's lawyer suggests he offer the cops the painting, which he doesn't have, as "a bargaining chip." Bernie retorts' "Suppose I gave them Judge Crater . . . or a this is jump for page 11 note: author id for page 10 cure for cancer." We like Bernie--his pals and his pluck.

Sometimes They Bite is another kettle of fish. This is Block's first collection of short stories, and most in this volume have appeared in either Alfred Hitchcock's Mystery Magazine, or Ellery Queen's Mystery Magazine. These tales all end with the "twist" that readers of these sister publications have come to expect. Many of the plots can be foreseen, in fact, though strangely, there is even some reader satisfaction in that. This is because Block is an extremely facile writer.

In the introduction to the collection, Block reports that most of these stories "were written between books, or when a work in progress had ground to a halt. Some were produced in transit, with the typewriter propped on a motel desk and the author confronted by his own unshaven reflection in the mirror that always hangs above those desks." None of that ever shows.

The brief introduction to Sometimes They Bite is extremely valuable, giving insight as it does into Block as creator. His particular brand of humor is also evidenced here. Consider the wonderfully farfetched comparison he uses when he tells us that short stories offer a respite from the business of writing longer pieces, for instance: "Novels are work and plenty of it, and there are stretches in most of them that are about as much fun for the writer as trench warfare."

This same introduction, by the way, answers both of the aforementioned Big Two questions. It not only gives us some idea how long it takes Block to write these stories, but, by giving Block's account of the incidents that inspired some of the tales, treats the "Is it autobiographical?" very nicely indeed.