As poet laureate of the United States, Robert Hass could sit back, field a few softballs tossed his way by the Library of Congress, and enjoy his well-earned title. But instead, Hass writes “Poet’s Choice,” a winsome and invaluable column for Washington Post Book World that has provided illuminating introductions to scores of poets. In his own new book, Sun Under Wood, Hass mixes prose with poetry in an idiosyncratically compelling style. Whether he’s writing of his mother’s alcoholism in “My Mother’s Nipples” (“In grammar school, whenever she’d start to drink,/she panicked and made amends by baking chocolate cake./And, of course, when we got home, we’d smell the strong, sweet smell/of the absolute darkness of chocolate,/and be too sick to eat it”) or the breakup of his marriage in “Regalia for a Black Hat Dancer” (“I don’t think I could have told the pain of loss/from the pain of possibility,/though I knew they weren’t the same thing”) Hass’ universal voice never fails to find your ear. Hass reads at 7 p.m. at Chapters, 1512 K St. NW. FREE. (202) 347-5495. (CP)