In the past, before Wanikani, I have use various textbooks (Japanese for Everyone, Japanese the Spoken Language, Minna no Nihongo, Genki, Tobira) and for anyone starting out I would recommend a textbook for grammar.
Right now I am taking a JLPT N2 prep course via Zoom in which we use:
- 新完全マスター文法 日本語能力試験 N2 (Shin Kanzen Master N2 for Grammar) - ISBN 978-4883195657
- N2 聞く (JLPT N2 Listening) - ISBN 978-4896894752
- 「かえるくん、東京を救う」(Super-Frog Saves Tokyo) - ISBN 978-4140351277
- Core 6000 website (iKnow!)
Starting from the N2 level, the 新完全マスター books describe Japanese grammar in Japanese (no English at all), and the vocabulary used in the example sentences and practice exercises is pretty difficult so I don’t really recommend it unless you are up for that.
N2 聞く is AMAZING! For each listening exercise it has the full transcript, lists a couple grammar points to take note of, and a couple vocabulary terms you might not already know. The dialogues are a good mix of formal and casual conversations, and grammar includes things that aren’t really “textbook” but occur often in real conversation like shortening endings of phrases. However, other than the English equivalents for vocab words this is also all in Japanese (grammar points explained with simpler Japanese equivalents).
かえるくん is published as a bilingual book (I think intended for Japanese trying to learn English) and filled with translation notes for each chapter. There are no furigana and kanji and grammar usage is a little advanced, but the teacher helps us with the parts we don’t get as we take turns reading aloud.
Core 6000 is one I would recommend adding to Wanikani for anyone of any level as it adds a lot of kana-only vocabulary you won’t see on Wanikani.