As a digital marketing manager trying to transition into a product marketing role, what books, classes, exercises, and projects would you recommend?

In 2011 I was doing online marketing for Salesforce and wanted to transition into a Product Marketing role. I applied and was rejected pretty quickly. I knew the hiring manager well and asked him what I could to do make myself more marketable. The first thing he recommend was to work on my presentation skills. That next Dreamforce I spoke twice at the conference and received high ratings. I suggest you find opportunities to speak in front of groups to hone your story telling skills, which will be very helpful as a Product Marketer. This practice ended up being especially helpful since later when I applied again for a Product Marketing role, the last stage of the interview was to take one of the Salesforce products and put together a deck talking about what's the next evolution of that product. I did well and was able to transition into a role in Product Marketing.

Product marketing is unique and I don't think there's one book you can read. Instead, I'd focus on learning more about the 3 things that product marketing touches: sales, product, and marketing. I'd read about sales to learn how to help reps close more deals. I'd read about product to help the product team build better products, but specifically hone in on the customer development side of things - and for marketing, I'd read every great copywriting and conversion books you can get your hands on.  Here's a list to get started: http://blog.driftt.com/12-books-that-will-make-you-better-at-product-marketing