Knowing that the addressee is Marie, and the gift a box of sugared almonds, you may say :
"Jean va lui en apporter", or :
"Jean va en apporter pour elle".
But never end a sentence with "en".
The construction of "Jean lui en conseille", when now you are speaking of books, is exactly the same.
You may sometimes change the order :
"J'en lui conseille" (but "Jean en" would be terrible for the ear).
"Louis en lui conseille" is better than "Louis lui en conseille" (for the same reason).
Other examples : "J'en lui sais gré", "J'en vous donne des exemples", rather classical but not obsolete, when you wish to insist on the indirect object and its proximity.
"Jean lui promet de lui en apporter" is not incorrect, but very inelegant, and suggests that the two "lui" are not standing for the same person. "Jean lui promet d'en apporter" is enough to guess that it's not for somebody else.