He takes advantage of OptiFine to vary the textures of many objects and blocks such as enchanted books, buckets or even animals and armor.
The author of the pack, SeaOfPixels, is assiduous, by that he means that he keeps updating his pack during Minecraft updates while bringing his personal touch each time. It’s one of those resources that, like the Minecraft Faithful or The F+ texture packs, don’t distort the default textures and just modify them to improve them. The New Default + pack stays true to the original Minecraft style and even boasts of improving it with better textures and new features.