The boss of SpaceX is reading a book from 1929, but old copies sold out shortly after their price soared to £75.
Second-hand copies of an out-of-print history book have soared in price from £4.50 to £75 after tech pioneer Elon Musk recommended it.
The boss of Tesla Motors and SpaceX told a Bloomberg reporter that he liked the book Twelve Against The Gods by William Bolitho, saying: "It's really quite good."
Bolitho, a South African journalist, profiled 12 great figures from history in the book, including the Prophet Mohammed, Casanova, and Napoleon.
Before Mr Musk's recommendation, just a handful of copies were trading on Amazon for about £4.50.
But just hours after his recommendation the price of copies of the book had soared to £75 per copy, and soon after there were no copies left at all.
Amazon's page for the book, which was first published in 1929, now reads 'Out of Print-Limited Availability'.
The English-language version of the book is also out of stock on a number of other popular booksellers websites.
On Amazon.co.uk, the book has just two reviews - both give it five stars.
One reviewer said: "You'll not likely find a more entertaining books of historical essays in modern print," while the other said: "I have had this book and re-read it off-and-on for years. The colorful details of their grand glorious adventures are wonderful."
Mr Musk is famously well read - he taught himself about rocket science by devouring books on the subject.
Now he reads more widely, and recommends his favourites from time to time.