Class Catalog from Crossplanes Game Studio brings a variety of racial classes to B/X Essentials, a grab bag of AD&D 2e races (aasimar and tiefling), 5e races (dragonborn and pixie), as well as variants of existing ones (dwarven thief, dwarven priest, elven rogue, halfling burglar), plus the gnome and half-orc.
The aasimar is basiclaly the offspring of a good outer planar being and a mortal, so it's not too surprising that its class is somewhat similar to a paladin, though being able to cure light wounds once per day instead of laying on hands. The tiefling, the opposite, offspring of a lower plane entity and a mortal is also more or less a fighter with some physical features (random) that might provide a slight bonus, like claws that do 1d4 damage.
Half-Orcs and Gnomes are also basically fighters, but the gnome does get to cast ventriloquism and later (at 3rd level) Phantasmal Forces once per day so there is a hint of the 1e fighter/illusionist. The dragonborn is basically a fighter that can also breathe fire twice a day (for a whopping 2d4 damage)
The Dwarven Priest and Dwarven Thief are more like single class versions, rather than a Fighter/Cleric or Fighter/Thief. Both only go to level 12 and more or less have the abilities of similar level regular cleric or thief, though the dwarf thief is much worse at climbing and slightly better at traps.
The Halfing Burglar is obvious basically just a thief, but can only go to 8th level. It's slightly better than a thief of the same level at hiding in shadows and picking pockets, but otherwise has the same abilities as a thief of the same level. It does also get the hobbit missile bonus and bonus to ac vesus larger opponents.
Pixie is perhaps the oddest class from the norm, but also a favorite of mine. The official version in PC1 Tall Tales of the Wee Folk has the Pixie as basically being a fighter, but with the ability to use magic items as a magic-user - wands and misc magic and such. This instead makes them magic users, more or less, (which is what PC1 did to sprites), only with a level cap of 8 (in PC1, Pixies and Sprites had no limits). The official pixie could fly, but only for a limited amount of time (3 turns) without needing to rest. This pixie can fly without any limit.
Besides the racial classes, there's also a new, option skill system introduced that works similar to saving throws. Basically characters are either trained or unskilled at something and roll a d20, modified by a relevent ability score. There's no skill list or anything, just a vague description of how it works and tables in the classes for the scores (there's not actually a lot of difference). Personally, I find the official B/X skill system superior, though that's not in B/X Essentials for some reason.
The art is color and isn't bad, but is somewhat abstract, having a few colors and seemingly little in the was of detail in the textures.
All in all Class Catalog isn't a bad attempt to fill in the holes that are left by the traditional B/X classes and found as B/X Essentials, and at $3.99, it's reasonably priced enough. But I think much like with B/X Essentials in general, you're better off going with the original alternatives, albeit spread over the various Gazetteeers. The original additions: tiefling, aasimar, and dragonborn aren't terrible, but also not very imaginative, all basically being variations on fighter.