For methods and processes to learn a new language, especially remembering grammar and conjugations, start with two classic books: "Fluent Forever" by Gabriel Wyner and "The Art of Language Invention" by David J. Peterson (though the latter is more about constructed languages, its memory techniques apply). These are not language-specific but teach universal principles like spaced repetition, mnemonic devices, and active recall. For practical grammar retention, look for workbooks that combine explicit rule explanations with spaced repetition exercises, such as those from the "Practice Makes Perfect" series (available for many languages) or the "Living Language" series. The key is to avoid passive reading; instead, use books that force you to produce the language actively.

Here is the honest tradeoff: No single book will make grammar stick without consistent practice. Books that claim to be "effortless" or "magic" are misleading. Effective methods require you to spend time on deliberate practice, like writing out conjugations from memory or using flashcards (digital or physical). For example, a good method book will teach you to create your own mnemonic stories for verb endings, but you still need to review those stories daily. The best approach is to combine a method book with a structured course or app that provides spaced repetition (like Anki or Memrise) and then apply it to real content (news, podcasts, or graded readers).

Concrete next steps: 1) Read "Fluent Forever" for its memory techniques and spaced repetition system. 2) Choose a language-specific workbook that has answer keys and exercises for grammar drills, not just explanations. 3) Set a daily routine: 15 minutes of active recall (writing or speaking conjugations from memory) and 15 minutes of input (reading or listening to content in your target language). 4) Use a flashcard app to review grammar rules and example sentences, adding your own mnemonics. 5) After two weeks, evaluate your retention and adjust the method if needed. Remember, the process is iterative; what works for one learner may not work for another, so experiment with different books and techniques until you find a sustainable routine.