Product is everything you could hope for from this topic.
PDF version is complete and text-searchable.
Print version is high quality and, to my mind, entirely interchangeable with the original book. Spine does NOT have any text on it.
Contents of the book cover everything you could want to know about the Cult of the Dragon - a full biography and multiple stat blocks for its founder, a full history of the cult including timelines and references to events in novels that featured them, dragons serving the cult, life as a low-tier cult member, hooks for adventures on behalf of the cult or thwarting it, and the traditional handful of new spells and magic items. If you're running an adventure featuring the Cult (for example the 5E Tyranny of Dragons adventures) or just looking to flesh out a campaign-level evil organisation for your Realms game, this book provides everything you want. It is, of course, set in the 2E era of the Realms, but the cult seems to have changed little in the 100+ years between that and 5E.
If you're not already interested in the Cult of the Dragon, your mileage may vary, but this material is still very easy to drop into any Realms campaign. Alternatively, it would require very little work to port some or all of it to any other setting where "wizards who worship undead dragons" is a concept that basically makes sense.