Wheelock is unbeatable for grammar and structure but it is dry.
Depending on what you are using it for, you would want different books as your second book. I enjoyed LINGVA LATINA by Vivarum Novum which is classic Dick and Jane type stuff but in Latin (you need a grammar like Wheelock or a professor with it since first page begins “Italia in Europa est Aegyptus in Europa non est” without translation). There are some specific to Ecclesial Latin, but I don’t have extensive experience.
One secret like any language is using it. I can read Latin since I do so every day with Liturgia Horarum but I stink at composition since I only reached over a paragraph once in composition.