I read this, and have nothing bad to say about it per se. I think Stoicism in the classic sense is very under-appreciated these days, and it's good to have a book to serve as an introduction. But I personally found it to be very repetitive. The historical context part is worth reading in my opinion, but apart from that you'd be better off reading something like Marcus Aurelius' Meditations instead, or some of the other classics.
Edit: Or if you're interested in a contemporary overview, I found AC Grayling's What is Good? to be much more insightful. Its central theme is also a search for some form of "philosophy of life", like Irvine's book, but it doesn't cover just Stoicism. Instead it covers many more philosophies, and I think it's a much richer book because of it since it gives you a much broader context, even if you end up adopting a Stoic outlook.