If you are Reformed, buy this!
This new printing was a very pleasant surprise as Ursinus' Commentary has been out of print for around 50 years, if I remember correctly. Used copies online have been priced between $70-$120 depending on the quality. This new print at the current price is an absolute steal. It's no surprise that it went out of stock so quickly. It might be a bit of hyperbole, but to me it's a truly historic moment that this work is generally available once again.
If I had to get rid of all of my books save one, this is the one I would keep. I have a bias toward Scottish theology, but Ursinus' Commentary is the most comprehensive summary of historic reformed doctrine in a systematic format that I have ever read. It can be heady at times, but its value cannot be overstated. I find myself referencing it often even since reading it all the way through several years ago.
Ursinus lays out many doctrines of the Reformed faith with stunning. He not only lays out the doctrines we affirm, but brings forth common objections (many of which we might still hear today) and answers them according to scholastic argumentation and scriptural evidence.