As rival tablets bite the dust faster than Audley Harrison the battle for top mobile reading device is again set to be a battle between the Apple iPad 2 and Amazon’s Kindle 3. The iPad is still way out in front in terms of popular interest, but the Kindle is catching up.

The Amazon Kindle dominates the eReader space, but Apple’s pricier and more functional iPad is also an excellent eBook reader – as long as you’re not outside in the sunshine.

This time last year – when the Kindle was launched – analysts at Experian Hitwise reported that there were four times as many internet searches for iPads as there were for Kindles.

Looking at the latest Hitwise search data the iPad is still the more popular product but the gap has narrowed between the two.

According to Hitwise both Kindle and iPad saw a 40 percent increase in searches in the busy post-Christmas period around Boxing Day and 27 December 2010.

Searches for iPads also increased dramatically in the first week of March 2011 when the iPad 2 was launched.

However, after the launch of the iPad 2 searches have flattened out and now iPad consistently receives twice as much search volume as the Kindle.

There is an interesting overlap in searches for both gadgets. Looking at all the searches for iPad and Kindle for the 12 weeks ending 30 July 2011, 65 percent of people searched exclusively for iPad, 27 percent searched exclusively for Kindle and 8 percent of people searched for both iPad and Kindle.

To look at the data another way: of all of the people who searched for an iPad during the 12-week period, 22 percent also searched for a Kindle, whereas of all the people that searched for a Kindle, 10 percent also searched for an iPad.

This core 8 percent demographic of people searching for both iPad and Kindle is an intense fighting ground for Apple and Amazon to win over new customers. Using Mosaic demographics Hitwise reports that three groups of people that are strongly represented in this middle ground are ‘Alpha Territory’ (60 percent more likely than the average Internet user to search for iPads and Kindles), ‘Professional Rewards’ (15 percent more likely) and ‘Liberal Opinions’ (21 percent more likely), three very affluent groups that are tech savvy and have a lot of disposable income to spend on gadgets.