Fellow Mac user here. I use Calibre as my default application and have been very happy with it. I only get in to the Connect Store app when I absolutely can't find a book anywhere else. It really depends on where you get your content from.
At the very least, you should download Calibre and give it a good playing with. There are lots of lovely features that, at the very least, are handy to have hidden away in you applications folder just in case.
Sony Connect email support link:
http://esupport.sony.com/US/perl/contact-email.pl