Tedious. Pohl take a valiant risk by introducing a huge chunk of astrophysics, but ruins it by foot-dragging aimed at keeping the reader "entertained". Of the Heechee series, this book stretches credulity the thinnest: the main character is a stored intelligence, psychic powers are a major plot point, godlike beings of pure energy who's origin predates baryogenesis living in black holes, etc. A good science fiction book tweaks one aspect of reality and explores the consequences; this book isn't all that good... It ends unsatisfactorily and pointlessly. A very direction disappointing for such a promising series.