Kurt Vonnegut can be harmful to your social life. So many people stumble across one of his novels, love it, and then spend much of their subsequent time acquiring the rest of his work, whilst persistently recommending others do the same with almost evangelical zeal. I too have been there.
So speaking as a fan, I'd have to say I was a wee bit dissapointed by Jailbird. It does have some of the virtues familiar to all Vonnegut's work: it's cynical yet compassionate, humanistic and a decent entertaining read. However, this bleak portrayal of people being lost and ignored among the ubiquitous forces of greed and corruption lacks the levity associated with much of the author's other work. I realise jokes aren't everything, but Vonnegut is often at his most incisive when mocking his targets with the aid of plenty black humour (as in Breakfast of Champions, for example).
So ultimately, Jailbird comes across as rather depressing. Perhaps it's because of the protagonist's perception of himself as a pathetically ineffectual nothing-man. Or perhaps it's because Vonnegut's pessimism got the better of him this time around.
Despite the above, I'd say Jailbird is certainly worth investigating, but if you aren't a fan of the author (yet!), it's probably best to start with another of his novels.