Unscrambled, these letters spell the name of an author of scary books for children.

The unscrambled name of the author is Robert Lawrence Stine, commonly known as R.L. Stine, who is famous for his children's horror book series, Goosebumps.

Here's how the statements align with him:

• True: Many of his books were centered on Halloween night (Many Goosebumps stories are set around Halloween).
• False: He only wrote joke books for kids (He is primarily known for his horror books).
• True: He is a British author (This is actually false; he is American, so this statement should also be adjusted).
• False: He wrote primarily for adults (He is primarily known for children's literature).

So, the final conclusion would be:

• He is a well-known author of scary books for children, but the claims about him being British or writing primarily for adults are incorrect.