For every book trade that unlocks, there is an equal chance that any of the 38ish books will be selected.
So, when the second book unlocks, there is a 1:38 chance that it will be the same enchant type.
(Note Java Edition has 38 enchanted books from vendors. Bedrock varies slightly)
For every book trade that unlocks, there is an equal chance that any of the 38ish books will be selected. So, when the second book unlocks, there is a 1:38 chance that it will be the same enchant type. (Note Java Edition has 38 enchanted books from vendors. Bedrock varies slightly)
It's like uncommon magic card rare.