Devices like Amazon’s Kindle have kickstarted mainstream demand for ebooks, but if Kindle is the ‘iTunes of electronic books’, where’s the Spotify equivalent? 24symbols is a new service which opens to all from today after a period in closed beta, offering on-demand access to a library of popular titles in a similar way to how streaming music services work.

Launching with a modest library of 1000 titles, 24signals features a range of classic books along with commercial releases from a number of small and medium-sized publishers. The idea is simple enough – you log in, look for a book you want to read and then… read it! Like Spotify, there are no restrictions – you can simply hop around between titles as much as you like. Facebook integration adds a social element, letting you get recommendations from your friends.

The product of a Spanish team, the Web-based service is working to a freemium model, offering a free, ad-supported version along with an ad-free option in return for a monthly payment prices at either €9.99 per month, €19.99 per quarter or €59.99 per year. The startup pays publishers based on how many pages users read from their books as a proportion of the overall number of pages read across all titles.

At present, 24symbols is entirely browser-based, and reading books on a computer monitor isn’t exactly an ideal situation. Luckily, an iPad app is due to be available in a few days’ time, potentially making this a really enjoyable way to enjoy and discover books. iPhone and Android apps are also on the way.

Screen shot 2011 06 29 at 15.27.34 520x255 24symbols launches as Spotify for books

The library’s current small size means that 24symbols can presently be largely viewed as a demonstration of its future potential. Co-founder Justo Hidalgo says that the company is currently finalising deals to bring more publishers on board.

However, it’s worth considering that in order to guarantee a decent level of revenue, 24symbols may have to work on the balance between the free and premium options. At present, the ads in the free version are simply too unobtrusive to encourage anyone to pay up, and subscriptions will definitely be more lucrative for 24symbols than ads. If 24symbols can get top-flight publishers on board, it would probably find itself having to lock the most desirable books behind the premium account paywall.

These are concerns for the future though, for now, 24symbols is a great first draft of what it could grow to become. You can sign up to try it right away here.

Screen shot 2011 06 29 at 15.32.21 520x375 24symbols launches as Spotify for books