Abdel Khalik Farouk said on Tuesday a Cairo court ordered his release, alongside publisher Ibrahim el-Khateib, pending an investigation into accusations of publishing “fake news”.
The book argues that el-Sisi lacks a vision for remedying Egypt’s economic woes, which Farouq blames on the military’s monopoly of power since 1952.
Copies of the economist’s book – titled, Is Egypt really a Poor Country? – were seized just days before his arrest on October 21, according to local media.
Farouk’s wife told Reuters news agency three policemen who came to their home said the arrest was in connection with the book.
She was later allowed to deliver food, medicine and clothes to him at a local police station.
Since el-Sisi came to power in 2013, human rights groups have accused Egyptian authorities of muzzling all dissent.
The authorities say they aim to fight against terrorism and the “spreading of false information”.