THE FLEET OF STARS, the final book of Poul Anderson's four-volume future history that began with HARVEST OF STARS, is perhaps the most successful. That's not saying much admittedly, but THE FLEET OF STARS leaves one with much fewer complaints than the previous books of the series.
THE FLEET OF STARS takes place over five hundred years after the previous book, HARVEST THE FIRE, and shows a far-future in which humanity is trapped in complacent irrevelance by the cybercosm, a collection of intelligent machines. Anson Guthrie, the libertarian icon and hero of the first book, leaves one of the distant planets he has colonized and returns to the Sol in download form to investigate rumors of a massive discovery by a gravitational lense.
This really is a mystery story, and although it drags often Anderson does manage to sustain suspense over what exactly the lense has discovered. The ending comes as something of a surprise. Unlike another reviewer, I felt the ending was particularly strong because it does answer the one question that the reader keeps in mind.
Although I cannot recommend this series, if you have already read HARVEST OF STARS and THE STARS ARE ALSO FIRE, it might be a good idea to read the latter two books of the series. While not as readable as airplane books or as substantial as real literature, this series does occasionally entertain.