The new Windows 11 Media Player does remember playback position for M4B files. It also displays chapter markers. However, it is buggy:
The best depends on whether you need a simple tool to open the file or a full-featured audiobook manager that remembers your place and handles chapters. M4B is the primary format for audiobooks because it supports chapter markers and bookmarking—features that standard music players often lack. Top Windows M4B Players (2024–2025) 1. Audibly (Best Specialized Audiobook Player) windows m4b player