Good news for those of you who love to listen to an audiobook before bed: Audible, the Internet’s number one digital audiobook provider, has just released a free iPhone application that works like a charm.

The app allows users to download audiobooks in-app over Wi-Fi and 3G (providing the file is less than 20MB), and then to open and listen to the books on their iPhone handset. Indeed, listening to audiobooks through the application couldn’t be more pleasant. We’ve seen audiobook-type apps before like vBookz that have literally read your books to you – with the listening reader following the text on-screen.

However, Audible refrains from encroaching into the eReader market, and simply sticks to what it knows. Instead of reading books to you, this application reads them for you, with each audiobook emotively reciting a story for its listener.

An obvious negative is that, while Audible’s app is free, its titles aren’t. As many of you will know, a subscription to Audible’s service is required – with its basic level setting users back somewhere in the region of $14.95 per month.

For this, don’t forget, users are treated to the “Audible experience.” The Amazon-owned company does sell brilliant audiobooks, and while vBookz offered titles for free, serious audiobook listeners will undoubtedly prefer to pay for the great service and great book performances they can get with Audible.

The application itself is a pleasure to use. Audible makes use of iOS 4′s multitasking, meaning that users can listen to an audiobook while using other applications on their iPhone.

In addition to this, a bookmark system means the application remembers where you left off when listening to your audiobooks. Resuming a book is quick and easy, and this makes interacting with audiobooks on your iPhone all the more enjoyable.

Users may recommend what they’re reading to friends via Facebook or Twitter, or personally through email. The app also works with other audiobooks in your iTunes library. However, as TUAW reports, certain aspects (such as chapter marks), don’t translate over.

So, if you’re an avid Audible user, be sure to download their free iPhone app now! And, if you’re not a current subscriber, head over to Audible’s site and take a look. The service is currently offering a discounted subscription fee (for the first three months) for new members – so check it out now!