Arcane Armoury Vol. 1 is a Dungeons and Dragons 5th edition supplement that you can download for free on the Dungeon Master’s Guild. The book is composed of two chapters of uneven length: a large one with 40ish new magic items, and a smaller one with a few special materials.
The selection of magic items in the first part of the book is truly spectacular. It ranges from nearly useless trinkets for an adventure, such as the Potion of Absolution which makes everybody forget you exist, to must have items, such as the Eyes of the Spectator which allow you to shoot beholder-like rays from your eyes. It also includes some funny magic items, such as the Claws of Chaos which turn your hands into ludicrous weapons, to near-artifacts with crippling side effects, such as the Circlet of Netherdeath which makes you immune to death at the cost of aging a year per day you wear it.
I was unimpressed with the second chapter of Arcane Armoury. The special materials allow you to tinker with non-magical items. You get a benefit in exchange for a penalty. For example, heavy armor made of Darksteel grants you a +1 bonus to AC but imposed a 5 feet penalty to your speed. There’s nothing inherently wrong with the special materials, I just find magic items more interesting!