I was 50 books behind on Terry Pratchett—36 “Discworld” novels alone—before he dropped his latest, Thud! It’s my own fault. For years, friends insisted that Pratchett’s books were genius, but I stuck with the more manageable Hitchhiker’s Guide and Red Dwarf series. Part of my aversion stemmed from the fact that humor and sci-fi are not natural allies. Any author taking a step too far in either direction winds up with an unreadable mess. But if 101 pages are any indication, Pratchett gets the mix just right with this one, adding—as all good humor and science fiction must—a touch of modern relevance. Thud! concerns a multimulticulti society whose “melting pot was full of lumps.” When a Pat Robertson– esque fundamentalist dwarf is killed, igniting centuries-old tensions between the dwarf and troll communities, a long-suffering police chief must solve the mystery, aided—perhaps—by the imp inside his Gooseberry personal Dis-Organizer. Only about 18,000 pages to go! Pratchett reads at 7 p.m. at Olsson’s Books & Records, 2111 Wilson Blvd., Arlington. Free. (703) 525-4227. (Dave Nuttycombe)