This topic has come up a few times before. One thread answered this question with remarkable detail but unfortunately I couldn't find it (sorry, reddit search function is not very good). I did manage to find this one though, and it touches on this subject:
Citation:
Jimmypickles. "Why was italy considered a weak and ineffective..." Reddit. Accessed December 7, 2015. https://www.reddit.com/r/AskHistorians/comments/3s0yvo/why_was_italy_considered_a_weak_and_ineffective/
Also so this post doesn't get deleted, here are some books on the subject:
Italy's Sorry by James Holland
Day of Battle by Rick Atkinson
Monte Cassino by Matthew Parker
Edit: I was mistaken. The link provided WAS the very thorough thread about his topic :)
FYI, you can get started on this topic with this section of the FAQ