If you can't find the GBE or want variety, these are comparable resources:
The Ultimate Guide to Gramática Básica del Estudiante de Español : Is the PDF Right for You? Gramatica Basica Del Estudiante De Espanol Pdf
Then it asks you to draw the timeline. Within 4 pages, you master a concept that usually takes months. If you can't find the GBE or want
"Ser is for permanent characteristics. Estar is for temporary conditions." (Then provides a list of exceptions). you see the rule.
The book is famous for its use of icons, charts, and color-coding. Instead of writing a paragraph explaining the difference between pretérito perfecto and pretérito indefinido , it uses timelines and arrows. You don’t read the rule; you see the rule.