The reliable Pew Internet Project has a new report. It finds the ownership of ebook reader hardware doubled in six months, from 6% to 12% of adults owning an ebook reader in the USA. It was based on phone surveys, and shows ereaders far outstripping the sales of the more expensive tablets PCs such as the iPad. However, the iPad2 wasn’t out when the survey was conducted. As with all such surveys, what really matters for self-publishers is not how many devices there are — but rather how many people are actively using them to buy books, how regularly, and the types and price-points of those books.