Terry Pratchett, the best-selling fantasy author, has struck a 10-book deal with Doubleday and Anchor Books, the publisher said on Sunday. The first book, “Raising Steam,” will be released in March as part of a seven-figure deal. Mr. Pratchett, whose books have sold more than 80 million copies, is known for his satirical series “Discworld.” Edward Kastenmeier, executive editor at Vintage Anchor, is the acquiring editor. “Terry’s work has a huge following and an enormous footprint in the fantasy world, as they were the first adopters of his enthralling, hilarious fiction,” Mr. Kastenmeier said. “With mainstream readers warming to the work of Neil Gaiman and George R. R. Martin, we see this as a crossover moment for Terry, an opportunity to expand his audience.”