Another large publisher has decided that ebook subscription services are worth testing out: Macmillan on Tuesday became the third big-5 publisher to make ebooks available on Oyster and Scribd, following HarperCollins and Simon & Schuster.

Macmillan is adding about 1,000 titles to both services. Macmillan CEO John Sargent had said in December that the publisher would test ebook subscriptions on “backlist books, and mostly with titles that are not well represented at bricks and mortar retail stores,” as a way of battling Amazon’s dominance in the ebook market.

Oyster and Scribd are vying for dominance in the ebook subscription market right now, alongside [company]Amazon[/company], which launched its competing Kindle Unlimited service over the summer. All three services are slightly less than $10 a month. So far, big-5 publishers are refusing to participate in Kindle Unlimited (like Macmillan, they see no reason to give Amazon a larger share of their ebook sales than…