Across from the comfy half-moon couch in a corner of this roomy caffeine bar hangs a large black-and-white drawing of a rhinoceros. The animal's eyes glare menacingly, and his nostrils flare. Hasn't had his coffee, obviously. Or perhaps he just hasn't found the right place to drink it. Relax, big boy, you're at Boomerang, which is a bona fide coffeehouse, the kind the Northern folks take for granted. There's conviviality between patrons and staff that makes this a warm place to come. There is, of course, the lengthy and varied menu of coffee drinks, from the basics -- a cuppa joe for $1.51 or a single espresso for $1.42 -- to the more specialized concoctions, like a white mocha, which is espresso, white chocolate, steamed milk, and whipped cream, for $3.35. But it's the atmosphere that makes this a "house." On a recent Saturday morning, a jazz guitarist set up his laptop computer, which served as a backup band, and then began strumming a soothing sound. One young woman read a book as she reclined on the sofa. Others chatted quietly at tables. Of course, the rhinoceros was none too happy with the whole thing. But what the hell; he's only a picture.