I just finished reading Existence by David Brin.
In the end I really enjoyed this one, although there was a period in the middle, probably about 40% of the book which I thought was very drawn out and I think could have done with some heavy editing. The early and late stages flowed really well and were interesting. Clearly, this novel was built from a range of ideas and short stories (the author admits as much at the end) and mostly it works well, but probably it needed some more chopping.
There is some very cool tech in this one. It's near-future, so nothing crazy, but some really good extrapolations of today's tech. In particular, I loved the smart network-integrated contact lenses which are where we'd like Google Glass to get to at some point. This integrated with sub-vocal commands and gesture and focal tracking for input which made for some really seamless personal technology. I enjoyed some of the discussion on how to deal with strong AI as it is developed, with the solution essentially to raise AI like children to teach them human values. There was one particularly cool piece of tech where a video of recorded events was played back at high speed, with an AI interpreting and summarizing the content in the sound, and then as the video was merged into real-time as the viewer caught up, the AI summarized less and less until just the raw feed was left.
Some things annoyed me. Perhaps I'm too sensitive about this, but there were a lot of new words created by taking existing words, and replacing vowels with 'ai', to mean AI enhanced versions of those technologies, such as ailectronic, vaice, aitopilot. They just seemed awkward and annoying to me.
There was a lot of discussion about two topics in particular that formed the main theme of the novel, and they are - coverage of possible extinction events, or problems leading to extinction, and also, the Fermi Paradox. Most of this was really well covered and if you are interested in these topics, then you will definitely enjoy this book.