story identification - Name the book where the setting is a giant ship with a planet inside

Here's what I remember:

• Takes place in the future on a giant, bigger-than-a-planet spaceship found and now run by humans


• Humans are genetically altered and/or are enhanced with nanotechnology and have essentially become immortal and can be healed from almost any wound


• The surface of the ship is inhabited by former humans who have mutated into a new species, and live their entire lives in a kind of space suit


• The plot involves the discovery of a small planet within the ship that the protagonist is stranded on along with many others, and they form a civilization and live there for centuries

Anyone know the name of this book? I can never remember it.

Answer

It's Marrow by Robert Reed. Good book.

When a jovian sized, artificially-created structure enters the galaxy, a society of technologically advanced humans (capable of interstellar flight and functionally immortal) are the first to intercept and investigate it. Finding it to be an intergalactic ship, they decide to convert it into a cruise ship, inviting alien races to join them in its massive, uncharted interior as it makes a slow circumnavigation of the Milky Way .

After thousands of years, with over 200 billion creatures living in its upper levels, a group of explorers discover a planet hidden in the core of the Great Ship. As they explore it, however, an ionic blast cuts them off from the rest of the ship and destroys much of their technology. Because this planet, Marrow, is slowly expanding, the explorers reason that a new bridge can be built in another 5,000 years. They thus begin a civilization on the surface of Marrow.

There's a sequel, The Well of Stars, and also a chapbook containing a novelette set in the same universe, Mere.