This is the 18th most frequent Spanish word.
entre
"Entre" means "between" or "among" in English.
Here, 'entre' is used as a preposition to indicate the position of the book being in the middle of two shelves, implying its spatial relation.
El libro está entre los dos estantes.
The book is between the two shelves.
In this sentence, 'entre' is used to denote a selection or a group, indicating that the suggestion is one of many options.
Entre sus sugerencias, la mejor fue visitar el museo.
Among his suggestions, the best was to visit the museum.
Here, 'entre' shows the context of a choice or decision that has to be made among several items.