The Crow Road by Iain Banks.
Middle-class Scottish lad, Prentice. Is having a tough time of it.
Failing his college course, constant arguments with his dad over their opposite political views, missing his brother who's star is on the rise in the world of stand-up comedy, not to mention the fact that he hasn't been laid in living memory !
Some years earlier, his favourite uncle disappeared one night in somewhat mysterious circumstances. There was a row between him and another uncle. After which he took off and hasn't been seen since.
His grandmother. A feisty, somewhat crazy old lady, asks him to find out what happened to her son. So, armed with nothing more than the pieces of manuscript his uncle was working on before he disappeared, Prentice tries to find out what happened.
Helped by his only friend, Ash. A lady with a great job and a 'thing' for Prentice. He sets off to find out exactly what happened.
if you want a visual reference, the BBC did serialize it back in the 90's.