"Eu consegui o livro."
Ive never seen that this way. Poder is used for asking for permission, also to show ability. But conseguir is used the same way referring to ability. "Eu posso dirigir" = im allowed t drive. "Eu consigo dirigir" = i can drive. I can read Portuguese = eu sei/consigo ler em Português. I can do that = eu posso/consigo fazer isso. I dont see any degree of capacity in this last example.
That's where it is confusing for me eu Posso - is I can, instead of, I am allowed... As taught here in the lessons; I posso = I can It was a teacher in a school who sad to me the easly done task is Eu Posso and something that requires effort is Eu Consigo (almost like i tried)
I hope it clears out where my confusion is coming from.
Dunno. If someones draws really well he says "eu posso/consigo desenhar muito bem" (and he doesnt need any effort for that). Poder is used for permission and abilities, while conseguir is just for abilities. "Não posso sair" (im prohibited to leave) "não consigo sair" (i cant get out/off - maybe the person is not able to open the door)