An alternative to the bonds are the books themselves. While the rare-book market has returned about 15 percent a year over the past two decades, according to David Brass, an antiquarian bookseller in Calabasas, California, returns have dipped slightly in recent years. But it’s too soon to say whether Fowler’s tomes will track the broader rare-book market. The closest comparisons are with Taschen’s Newton and Ali books. Since its publication, Sumo has roughly quadrupled in value; GOAT hasn’t appreciated.

For buyers who wish to protect their investments, Fowler offers insurance plans and humidity-controlled storage vaults. That suits Murali Ramachandran just fine. The 40-year-old trader at Viper Capital, a London hedge fund, says that after ordering 15 copies of Kraken’s forthcoming Formula One book, for about $600,000, he plans to stash them away and “see what happens. It’s a bit of an experiment, but in terms of the money involved, it’s not like I’m betting the house on it.”

Passion PlaysHobby investments had been crushing the Dow—and that was before Wall Street’s summer swoon.
Tracking the performance of assets like coins and violins isn’t like following stocks; the most widely recognized ­indices for collectibles are published just once a year. This table shows the ­return on investment over the most recent five-year period for which comparable data are available: May 2002 to May 2007. —Jen Itzenson