You can buy an e-ticket here. You can also do this at the museum. E-tickets do not entitle you to fast access and you still have to have your e-ticket scanned at the pay desk. Please note that on Saturday or Sunday afternoon the museum can be busy and there will be a queue. If you have a Museum card, Stadspas, ICOM card or iAmsterdam City Card, you do not need to purchase an e-ticket.