Holiday is the most widely read Stoic writer of the contemporary period. The Obstacle Is the Way (2014) is built on a single line from Meditations 5.20 — the impediment to action advances action; what stands in the way becomes the way — and turns it into a working philosophy of resilience for entrepreneurs, athletes, and military leaders. The book has been adopted by NFL teams, Special Forces units, and Silicon Valley founders. Its commercial reach is unprecedented for a book of practical Stoicism.
The serious Stoic reader has a complicated relationship with Holiday's project. The reach is real and the gateway function is real — for many contemporary readers, The Obstacle Is the Way or The Daily Stoic is the door through which they first encountered the tradition. Once through, they go to Robertson, Pigliucci, the ancient texts themselves. As an onramp, Holiday is the most effective writer the tradition has ever had.
The criticism is also real. Holiday tends to dissolve the specific Stoic doctrines into generalized resilience advice — the harder commitments (the theology, fate, preferred indifferents, cosmopolitanism) are typically absent. The result is Stoicism as productivity tool, defended on the grounds that the productivity tool is internally consistent. For readers who want the tradition's full system, the lossy compression is a problem. For readers who want a workable practice tonight, the simplification is the entire point.
The Daily Stoic is the most useful of his projects. It is 366 short passages — one for each day of the year — with two paragraphs of Holiday's commentary. The selection is sound, the commentary is plain, and the daily format gives the reader a long-term scaffold of exposure to the corpus. The daily email of the same name has done more for modern Stoic reading than any other single ongoing publication.
He is also a useful counter-example for how to read modern Stoic writers. Read him with the awareness of what he has flattened, and you will find both the practical bite and the doctrinal absences. His best service to the tradition has been to recruit readers who would otherwise never have heard of it. His worst service has been to teach some of them that the recruitment was the whole curriculum.