"She reads him a book."
Translation:Ela lê um livro para ele.
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)