Whilst this is a brilliant book by Vonnegut and deserves 5*, I have previously read Breakfast of Champions and Slaughterhouse 5 - in my opinion, they are much more accessible and broader than Sirens of Titan. If you haven't read Vonnegut before I suggest you start with one of those rather than this, come to this afterwards.
This book concerns Winston Miles Rumfoord who gets caught (with his dog) in a time anomoly (a chronosynchlastic infundibulum) where he is held outside of time. He materialises on earth periodically at the home of his wife (very privately - no one admitted) but on one occurance he invites a playboy Malachi Constant to attend one of these materialisations. He informs Malachi that he will travel to Mars, Mercury and Titan and that Malachi and Rumfoord's wife Beatrice will have a son Chrono. Both Malachi and Beatrice try to prevent the future, but circumstances work against them and end up on Mars, and eventually end up on Titan.
On Titan is a stranded being, Salo, from Tralfamadore, waiting for a spare part for his spaceship to enable him to carry on his journey. He has been there for over 200,000 years watching the Earth and waiting for a message from home. Some areas were clearly inspiration for Douglas Adams Hitchikers Guide to the Galaxy.
This satirical SciFi book explores religion, the hand of God, circumstanses, manipulation and control - it is disturbing in parts and amusing in others. I really enjoyed it!