Beyond the Blue Event Horizon is a sequel to Gateway which I read (warning - spoilers) at the beginning of the year. Beyond follows the characters from the first but, if you haven't read the first, that probably doesn't help that much so I'll give a brief outline of the universe in which these books are set.
Humans made their way into space, where they discovered the remnants of an ancient, super intelligent civilization. Gateway is an asteroid from which people can launch into space in hopes of finding even more technology and thus becoming extremely rich. Unfortunately, many people simply don't return from these flights. In the first novel, Robinette Broadhead heads to Gateway to try his luck, and the sequel continues his story.
As I was adding this book to my "currently reading" section on Goodreads, I noticed a link to the author's (Frederik Pohl) blog. I love the idea of authors blogging, especially if they have lead as interesting a life as Pohl has. Definitely check it out of you are a sci-fi fan.
Speaking of being a sci-fi fan, you really need to be one to even consider reading this series. While there are certainly elements that anyone could enjoy, such as the clever exposition in the first, it requires far more willingness to get into the geeky sci-fi realm than a book like Dune. Plus, it is the ideas of the book that make it worth reading, and if you aren't into concepts such as faster than light space travel, black holes, and crazy theories about the creation of our universe, you simply won't have a good time reading it. That isn't to say the writing is bad, it's quite good in fact, it just isn't so earth shatteringly amazing that everyone who has the ability to read should pick up this book right now.
People who should pick up this book (or at least the first) are those who enjoy asking the question "what if there were aliens? what would that mean? How does our humanity change or become more evident when faced with creatures and ideas that are difficult to even imagine?" These are cool questions, and Pohl handles them with skill.
"All myths and deities are tolerable enough to believe in; but what if they become real?"(76)