Python for ArcGIS is a book that I have been looking at. Does anyone know if this would be applicable in QGIS? I am not looking to write application/plugins, simply get better at understanding expression etc. for standard workflow. e.g. queries and data-defined settings.
The PyQGIS cookbook is a great resource
While this book is not specifically QGIS and Python, it was written for open source coding using GDAL and OGR with Python: http://www.packtpub.com/python-geospatial-development/book
The PyQGIS 101 tutorial aims to help GIS users to get started with Python programming for QGIS 3: