Hi, bobsi18. Happy birthday! Glad you are enjoying your new Sony!
I use a Mac too. You can install Adobe Digital Editions on your Mac. It will read DRM'ed ebooks ok on your computer screen. The problem is it doesn't recognize the Sony ereaders as a device connected by USB. It's invisible. ADE for Mac recognizes other ereaders (like the Nook) but not Sony unfortunately. Therefore you can't use ADE to transfer books to your Sony. That's ok. I use the Sony Reader Library software to import DRM'ed books and transfer them to my ereader. You can use the Sony software to manage all of your ebooks if you want. It can handle both DRM'ed and non-DRM'ed and not just ones that you purchased from Sony.
I like summaries at the beginning of my books too. Here's how I add summaries for my non-DRM'ed books. In calibre, I paste summary text into the Metadata field called "Comments". Then when you do a file conversion, in the Structure Detection input check the box for "Insert metadata as page at start of book".