Which books/articles by Fr. Matta are the ones that are attacked/controversial?
Also, what are the charges brought up against Fr. Matta?
You can start with the list I gave you in the topic "Why do we sin" in the "Free-for-all" forum until I come up with a translation of a list of Matta's errors in all his books. They are numerous, so please be patient.
As for charges of misconduct and attacks against the Church, one has to consider his whole "career" as a monk to come up with a conclusive answer. You would have to examine the position of St. Macarius monastery in the Coptic Church after Chalcedon and the burning of the Alexandria library and school of Theology upon the arabic conquest,and how this great monastery has been transformed under the spiritual guidance of Matta El-Maskeen. You can visit the monastery and come up with your own assessment after you see the huge industrial advancements at this monastery and get an idea of the monks' routine, and compare it to other monasteries. Matta's life becomes very interestings if you consider his relation to President Saddat before and after 1981, his defeat at Papal elections twice, him being offered the Papal position by Saddat after the lawful Pope, H.H. Shenouda III was imprisoned in his own monastery, and how the synod refused such consecration and only to see them persecuted by Saddat, who wanted to go with the plan to split the Church anyways but got stopped because Khaled El-islambuli and Atta Tael assassinated the man, splitting him in two from the waist. If you consider the book " Church and Social service", in which he accused the Church of conspiracy and treason and caused the imprisonment of a popular Bishop, Samuel the Martyr, in Nasser's regime, together with the above, you will understand why Copts in Egypt have little respect for the man, and why his majority of vocal fans is in the diaspora.
We usually come up with totally different views, so you are on your own in studying Matta's life so you can come up with your own conclusions.
What books/articles have been written against Fr. Matta?
Articles by H.H. in El-Kerazah magazine and seven books published against the heresies of Matthew the Poor. Will prepare a list of them later.
Is there a way where I can get any of those books?
I am not sure how far the translation of Matta's books into English have progressed. As for arabic books, you can always find them at the monastery of St. Macarius at Wadi El-Natron in Egypt and the last time I checked they were available in an independent bookstore called El- Ma7abah. It is one of the biggest christian bookstore in Egypt.