There are reputable courses that are based on normal academic reading theories, such as
Purpose of reading & Speed vs Comprehension
Keyword reading / Skimming
Scanning and the formatting of material
Practicing under timed conditions
Some of the explanations used to promote less reputable courses include theories from popular psychology, urban myths about the brain and pseudo science
These concepts include:
Cyclopic perception (peripheral vision for reading)
Cerebral hemisphere differences
Paraconcious processing
Visual reading
Auditory reading
Word awareness
Cognitive window
Context pool (Speed Reading Made EZ)
Subconscious Photo programming