Reading the delightful and surprisingly easy al- Falsafah al-lughawīyah wa-al-alfāẓ al-ʻArabīyah (pdf) from the collection of over 15,000 Arabic books NYU is working on making available in digitized format online.
Another book worth spending the weekend reading is al- Muʻtazilah by Zuhdi Jār Allāh for those who are interested in a historical account of the Mutazilites.
The dedication reads:
'To young Arabs calling for freedom, in every place and throughout time, I dedicate this dissertation on the history of the advocates of freedom of thought who came before them"
That alone makes it worth the read.