It's pretty much a reworking of the (far better written) Across A Billion Years, by Robert Silverberg. There are points (unmemorised - this is a book you'll have fun reading but are unlikely to want to re-read) that are jaw droppingly poor but for the most part it's a competent, unremarkable romp. Nice attempt to make the alien alien, we don't see enough of that. But if you can only read one "on the trail of a lost ancient alien civilisation" book then you'd be mad to read this and not Silverberg's. But you can read them both, and hey, for a buck....