You could do a lot worse than having Garrett Oliver as a drinking buddy on a rainy Wednesday night. But that’s what’s in store tonight at London Grill. The Brooklyn Brewery brewmaster and authoritative author of beer books will be hanging out, rapping about beer and enjoying a few rounds. Well, he’ll also be hawking his new sudsy tome, The Oxford Companion to Beer, which he will have in tow. And London will have some of his finest on tap, including Brooklyn Black Ops, a bourbon barrel-aged stout, as well as Companion, a wheat-based barley wine from the Brooklyn Brewery Brewmaster Reserve series. The beer starts flowing at 7 p.m.