"She reads him a book."
Translation:Ela lê um livro para ele.
It seems to be 'o' sometimes and 'lhe' sometimes. Are they interchangeable? E.g., should Ela o le um livro be ok?
it depends on the verb.
Basically, the forms "lhe" and "lhes" replace indirect objects started by the preposition "to". Now the forms "o" and "a" and their plurals complete direct transitive verbs.
The pronoun 'o' is a direct object, and 'lhe' is an indirect object, so they're not interchangeable. Regarding the verb 'ler', "você lê alguma coisa para alguém" ("you read something FOR somebody"). We don't use to say "lê-lhe".
I think that whether it is o (him) or lhe (to him) depends on the verb, I don´t think theres any rule, or that it translates directly from English, but that it´s just a case of learning them all.
e.g this one. Ela lhe lê um livro = She reads (to) him a book...
I think se is ¨oneself¨, as in ¨¨ela se senta¨ -> she sits (herself)