For people interested in what meditation really "is," at least from a Buddhist perspective, Ven. Thanissaro is worth a look. Among his many excellent books is Right Mindfulness: Memory & Ardency on the Buddhist Path

> For the past several decades, a growing flood of books, articles, and teachings has advanced theories about the practice of mindfulness which are highly questionable and—for anyone hoping to realize the end of suffering—seriously misleading. The main aim of this book is to show that the practice of mindfulness is most fruitful when informed by the Buddha’s own definition of right mindfulness and his explanations of its role on the path.

https://www.dhammatalks.org/ebook_index.html#right_mindfulne...

His approach got me past some serious blockages in my practice.