Marrow

Marrow by Reed, Robert. mass_market edition. ISBN: 9780812566574.

The Ship has traveled the universe for longer than any of the near-immortal crew can recall, its true purpose and origins unknown. It is larger than many planets, housing thousands of alien races and just as many secrets. Now one of those secrets has been discovered: at the center of the Ship is . . . a planet. Marrow. But when a team of the Ships best and brightest are sent down to investigate, will they return with the origins of the Ship--or will they bring doom to everyone on board? Robert Reed, whose fantastic stories have been filling all the major SF magazines for the past several years, spins a captivating tale of adventure and wonder on an incredible scale in this novel based on his acclaimed novella.