<p>The Barron’s 2400 writing section is useful. The questions are extremely hard, that’s for sure. </p>
<p>If you need a back-to-basics, grammar 101 course, you’ll want the regular Gruber’s book (not the 2400 book). It has an immensely detailed and useful 50+ page review of English grammar :D. The Barron’s 2400 book only skims over grammar.</p>