If you walk down Mt. Auburn to Penguin Books, stop at McIntyre and Moore on the way. There are two McIntyre and Moore shops, and they are quite different. The old small one (30 Plympton St.) carries rare, out-of-print books. It is old and dusty, and full of atmosphere, but doesn't always have much to buy. It is definitely worth a visit, though.

The new store (8 Mt. Auburn St.) is huge and seems to have everything. It's the kind of store you have to browse in to find anything, but it is also the kind of store you want to browse in. It calls to mind the old bookstore at 18 Charing Cross Road.

If McIntyre and Moore is old and full of atmosphere, the newest addition to the Sqare's seemingly endless supply of bookstores, Barillari Books (One Mifflin Place), is just the opposite.

Barillari is a disappointment. Cool grey and green inside, with an espresso bar, it gives a good first impression. But its selection is meager and confusing.

It stocks a huge supply of coffee table books, and has a good children's books section. As well, it is another strong fiction store and the paperback books are discounted 10 percent.

But that is the best it can boast. Perhaps its beginner status makes it less polished, but there is something almost confrontational about Barillari. You feel reluctant to buy anything, but guilty if you don't, as four different salespeople watch you all the time.

It's worth checking out if the other stores don't please you, but there is no real reason to go to Barillari, unless you're in the neighborhood. The other stores have everything this one offers, and they are all closer.

There are several "specialty" book stores in the Square if the more general ones don't carry what you are looking for. Grolier Books (6 Plympton St.) has 9000 poetry titles, and carries books, cassettes and magazines about poetry as well. Asian Books (12 Arrow St.) has a remarkable selection of books on Asian and Islamic culture.

Science Fantasy Bookstore (8 JFK St.) carries new, used and out-of-print science fiction. Seven Stars (58 JFK St.) and Sky Light Books (111 Mt. Auburn St.) have new age books and crystals. Both of them also offer classes and workshops in new age philosophy. And The Thomas More Bookshop (1352 Mass. Ave.) carries books in philosophy and religion.

There is clearly something for everyone in at least one of Harvard Square's many bookstores. It depends what you are looking for. It can't hurt to spend a day shopping bookstores before you shop for books.