Breach of Promise by Perri O'Shaughnessy is a little reminiscent of John Grisham's books with a similar legal mystery format. Note: Perri O'Shaunnessy is the pen name of two sisters.
The story was well developed, but I did find it a little tedious at times and not overly believable, especially the penultimate chapter. At over 500 pages, I felt it could have been condensed considerably without losing the story or legal action.
From the cover:
In glitzy Lake Tahoe, couples break up every day. But few are as successful as Lindy and Mike Markov, who built a $200 million business together before Mike took up with a younger woman. Now he's claiming he doesn't owe Lindy a dime since they never married. Attorney Nina Reilly, struggling to make a living in her one-woman office and raise a young son alone, agrees to take Lindy's case. Nina knows winning is a long shot, even with a brilliant jury consultant and a palimony expert on her side. It's the kind of case - full of passion and explosive secrets - that could make a fortunate for a young lawyer. Or drive someone to commit murder - for love, money or the right verdict.