Small towns breed big obsessions. Case in point: Falkirk's Martin C Strong. After all, the 44-year-old has devoted half his life to music, a passion that takes form in his Great Rock Discography. An A-Z of the recorded output of more than 1,200 artists, everything about the book is big. The latest edition weighs in at a massive 1,730 pages (1,749 if you include the preface and introductions) and more than 5lbs.

Actually, Strong describes what he does as being only a job. Well, yes, but it's a ''job'' that requires a junior doctor's working hours (70 a week - ''it digs into my social life a little bit'') and offers no more than an ''average living'' in return. Sounds a bit like obsession to me.

And it's an obsession that started early. Strong bought his first album when he was 12 - David Bowie's Aladdin Sane, in case you're wondering - but even before that he would listen to the chart countdown during school dinnertime and write it down. ''It carried on to the first period after dinner. School wasn't going to get in my way. I needed to get numbers five down to one.''

Such behaviour may explain why Strong left school with just the two O grades. He went through all kinds of jobs - labouring, sales, deliveries - but none of them stuck. ''I tried everything, but I wasn't happy with anything - and they weren't happy with me.''

But he had always religiously recorded the details of albums he listened to, and eventually someone suggested he turned those details into a book. ''I thought, 'Well, why not? I'm not doing anything else. While I'm looking for a job I might as well keep this going too.'''

That was 1982. For a few years he treated the project as a hobby, but his mum's death in 1985 spurred him on to take it more seriously. ''It did seem to kick me up the bum to get things done rather than just saying I was going to do it.''

It took another nine years before he made it into print. He took the manuscript to a couple of London publishers but they couldn't get past the fact that it was handwritten. In 1990, though, Canongate decided to take a chance - and four years later the first edition appeared.

These days Strong is as keen on the writing as he is on the music. He wants to branch out and has even written a play, but he's not giving up the (all) day job just yet. Fans wouldn't let him.

''I've got 1,000 letters over the last ten years,'' he says. ''Most are congratulatory, which is great. The rest ask why Cliff Richard isn't in there.'' n

The Great Rock Discography, Seventh Edition, is published by Canongate on October 21, priced (pounds) 25.