Textbooks (leerboeken) provide structured progression that self-study otherwise lacks. For complete beginners: Colloquial Dutch (Routledge) gives solid grammar foundations with audio. Assimil Le Néerlandais (if you read French) is exceptionally efficient. Teach Yourself Dutch is accessible and includes cultural context. Woordenlijst Nederlandse Taal (Green Book) is the official Dutch spelling dictionary — essential reference, not a learning textbook.
Intermediate textbooks: NT2 series Nederland in Zicht (a/b) is used in formal integration courses and is well-structured for B1-B2 progression. Taal Vitaal is another common coursebook used in Dutch language schools. For grammar reference: de Kleine Woordengrammatica (small word grammar) or Grammatica van het Nederlands (more comprehensive). Taaladvies.net (the official language advice website of the Dutch Language Union) is invaluable for settling grammar and spelling questions.
Graded readers: the most useful reading materials at your level. Nederlandse sprookjes en verhalen (fairy tales — A1-A2). Easy Dutch Reader (A2-B1). De geheimen van het Gravenhof (mystery story, B1). Brugklasgeheimen and other Dutch young-adult fiction (B1-B2). At B2 and above, move to authentic Dutch novels — Annie M.G. Schmidt for charm, Tim Krabbé for literary suspense, Maarten ‘t Hart for dry Dutch humour. A reader you enjoy finishing is worth more than a textbook you abandon on page 40.