It can be surprisingly difficult for authors to know how well their books are selling. Amazon doesn't give out sales figures but it does provide a sales ranking, which at least gives you some idea how your book is fairing in relation to some of its competitors, so I like to keep an eye on how mine are doing.

I'm pleased - and slightly surprised - to be able to report that after a couple of weeks on sale, my book on the DFV F1 engine has raced into Amazon's best-selling motor sport books. Meanwhile, The Classic Car Book - which came out last year - is right at the top of Amazon's list of best-selling classic car books.

Positive reviews of both books can't have hurt. Autocar's Steve Cropley gave the DFV book the thumbs up in his column the other week, while Rosie McMahon was equally approving in Motorsport News. Meanwhile, the reviews page of Motorbar.co.uk described it thus:

Bit of a surprise, this one... I expected to find something rather boring and technical. Not so... there is such a wealth of anecdotes, interviews and many archive photographs (some previously unpublished) that there is enough to keep you focused — even if you find facts and figures a bit hard going... Worth investing in, even if you have only a passing interest in motor racing, The Ford Cosworth DFV is a fitting tribute to the most successful Formula One engine of all time.

How long this run of success will last is anyone's guess, but even if it's short-lived it means I can now describe myself as a 'best-selling author' - as long as I don't look anyone in the eye while I say it...