The literary equivalent of an musical b-sides and rarities compilation, this is a collection of musings on, and extracts from, early versions of the novel of '2001' - Clarke directs the reader to Jerome Agel's then-forthcoming, now-equally-out-of-print 'The Making of Kubrick's 2001' for information on the making of the film. As such, your enjoyment of this is going to depend on your opinion of Clarke's novel (which, without the film, would probably be out-of-print too), and whether you want to read disjointed chapters from early drafts. As glimpses into an alternative '2001', one that Kubrick might have filmed, it's priceless; as entertainment, it's less interesting. Like the other 'hard sci-fi' writers, Clarke is best at the science bits, and a short segment from an alternative finale, one in which the four surviving Discovery crewmembers explore a deep hole in the side of Iapetus (although, oddly, it's only referred to as 'Jupiter V' - perhaps they hadn't named it yet), is fascinating. The talky bits were never his strong point, though, and the pre-flight glimpses at Earth in the year 2001 are full of people not so much conversing, as delivering little scientific monologues at each other. As with everything else Clarke has written, none of the characters have any actual character - although it's possible that this is hyper-realism as, let's face it, most people in the real world are bland, dull and interchangeable, especially when they're at work, and Clarke's characters are always at work. Disappointingly, HAL doesn't appear at all. The other main strand personifies the monolith in the form of Clindar, a tall, noble alien who comes across as an insufferably self-righteous riff on Klaatu from 'The Day the Earth Stood Still'. One shudders to think how camp the film would have been if this had been filmed. And there are a couple of descriptions of alien landscapes and societies which are quite evocative but have a habit of repeating themselves.
There's a reprint of 'The Sentinel' as well, but if you're going to the trouble of ordering this from Amazon (it took about a month for them to find and post it to sodden, freezing, miserable London, which wasn't much slower than a normal order) you've probably read that already. In summary, then, if you're reading this you're either buzzing with curiosity or you're me, and if you're a fan of the film, the book, or Clarke it's essential. You'll probably buy it, read it once, and never read it again, though.