The NASB is an excellent Bible for serious study as it is word for word literal translation, sometimes too literal and stilted for public reading.

Many times idioms are translated to their English meaning. All languages have idioms (figures of speech). For example, one may say that one is "hitting the sack". But to someone in China, they may not understand that you mean you are going to bed. Same goes for Hebrew and Greek. At least twice in the Old Testament, it is said that one "covered his feet." That's a case where a clearer rendering is better than a strictly literal one. We may think that he is warming his feet with a blanket. The covering of his feet is a Hebrew idiom, an euphemism meaning "dropping his garments to his feet in order to relieve himself." Translating that idiom as "relieving himself" into the text is preferred, and placing the Hebrew idiom in the footnotes. The NASB places literal translations of idioms in the footnotes several hundred times when it would be confusing to English readers if placed in the text itself, and places the English meaning in the text and the NASB still retains the properties of a literal translation. This is done in the NASB more often than the English Standard Version, and makes the NASB slightly easier to understand than the ESV.

My only disagreement with the NASB is the verses on the exception of a divorce in Matthew 5:32 ("unchasity") and Matthew 19:9 ("immorality") The same Greek word, porneia, is used in both passages, and means a sexual sin. Immorality can mean all kinds of sinful behavior. The NASB dropped the ball here.

I would highly recommend the NASB for serious study and reading, as long as they are aware of the mistake in Matthew 19:9.