I've read:

Queen of Scots: The True Life of Mary Stuart - John Guy
The Highland Clans - Alistair Moffat
In Freedom's Cause - G.A. Henty
Scotland's Story - Tom Steel

Any additional recommendations?

Particularly interested in finding a great book about Robert the Bruce

Not quite in the era you're looking but I found this book extremely interesting.

Here's a couple of my favorites:

A Military History of Scotland by Edward Spiers

Union and Unionisms: Political Thought in Scotland, 1500-2000 by Colin Kidd

Inside the Divide: One City, Two Teams, The Old Firm--Richard Wilson

"The Wallace" by Blind Harry dates to about 1488
and has been the basis of several popular books and movies.

Read through three historical fiction books that I thought lead to a better understanding of the eras....

Why We Don't Kill Spiders: A Tale of Bannockburn - Bo Macreery
Mad King Robin - James Vella-Bardon
The Bookseller of Inverness - S.G. Maclean

The first two ended up being remarkably similar - of the two I would pick Why We Don't Kill Spiders.

The third was my favorite of the bunch.