The coLanguage Academy Dutch for beginners book is not widely recognized or reviewed, so it's hard to guarantee its quality for a true beginner. Instead, consider well-established titles like "The Routledge Intensive Dutch Course" for a thorough grammar foundation, or "Colloquial Dutch" for a practical, self-study approach. Both are designed for English speakers and include audio resources, which are crucial for pronunciation.
For your girlfriend in Indonesia, a book with clear explanations and built-in audio is essential, as she won't have daily Dutch immersion. "Essential Dutch Grammar" by Henry R. Stern is a compact, no-nonsense reference that pairs well with any main coursebook. Another strong option is "Dutch for Dummies," which breaks down concepts into manageable chunks and includes a CD. Avoid books that are purely phrasebooks or lack exercises; they won't build real proficiency.
Tradeoffs: "Routledge" is more intensive and academic, better for someone who enjoys structured study. "Colloquial Dutch" is more conversational and paced for self-learners, but may skip some grammar depth. "Dutch for Dummies" is very accessible but can feel too simplified for long-term progress. The best approach is to combine a coursebook with a grammar reference and a separate vocabulary builder like "501 Dutch Verbs" for verb conjugation practice.
Concrete next steps: Check reviews on sites like Amazon or Goodreads for the latest edition. Look for books that explicitly mention audio CDs or downloadable MP3s. Since you'll visit her soon, bring the book and also set up a weekly video call to practice speaking together. Supplement with free apps like Duolingo for vocabulary drilling and YouTube channels for listening practice. Avoid any book that claims to make you fluent in a month; language learning takes consistent effort over time.