Over 1.5 million public domain books in the United States are now available for bookworms who have iPhones or Android-enabled devices.

Users can go to http://books.google.com/m on their mobile browser to search for a title, author or subject and start reading while on the go.

Additionally, users can browse the list of "Featured books" and various categories such as business and economics, the Classics, science and math, and travel. Once they have picked out a book, users can easily get back to their selections by clicking on the "Recently viewed books" under the "My books" section.

Books were already available on Google Book Search. These new mobile editions are optimized to be read on a small screen.

Google Book Search previews are composed of page images made by digitizing physical copies of books.

The page images work well on a desktop, but don't work well when viewed on a phone's small screen.

Google's effort to make these books accessible is to extract the text from the page images so it can flow onto a mobile browser just like any other Web page.

The process is known as Optical Character Recognition.

Additionally, Google's computer algorithms automatically determine the structure of the book.

With this launch, the Google mobile team believes it has taken an important step toward more universal access to books.

However, placing books on mobile devices isn't a new idea.

Books that Amazon.com Inc. sells for its Kindle electronic reading device will soon be available on mobile phones as well.

The Seattle-based online retailer is working on making Kindle books available on a range of mobile phones.

Another ebook provider, Mobipocket, which is owned by Amazon, already sells titles that can be read on numerous smartphones.

Audible.com, another Amazon property, already sells its audio books for iPhones.

Amazon is widely expected to unveil a new version of the Kindle device at a news conference Feb. 9 at the Morgan Library & Museum in New York.

Meanwhile, to celebrate its 60th anniversary, romance series book publisher Harlequin Enterprises Ltd. has released 16 free romance novels for users of Lexcycle's Stanza electronic book reader application for Apple's iPhone and iPod touch (see story).

Stanza for the Apple iPhone and iPod Touch is available as a free download from the iTunes App Store and from http://www.lexcycle.com. More than 1 million users have downloaded Stanza since mid-July, when it debuted in the App Store.