Barnett's commentary on Mark is more than just a commentary. It a good read as well. The chapters are broken up into nice chunks and filled with helpful information on the original Greek as well as historical and cultural background. Barnett is very good at reminding the reader of the general themes that are carried through Mark, bringing out significance in the context of the book and in the bible as a whole. The questions at the end of each chapter are actually really helpful (so many books with questions are just pointless) and it will be great to turn back to whenever I study Mark in the future.
I would recommend this book to anyone who wants to study deeper into Mark. Very good, will buy more books in this series.