Don't know about the Mariners
Learning System, but I started by using a book called "Get Your Captains License" by Charlie Wing. It has a CD with it that generates random tests from the USCG database of questions. The book was pretty good and the CD was very helpful. I studied the book and CD on and off for about a year and it was pretty tough to study from (at the time I had been sailing for more than 20 years). The problem is that you are prepping to take a test from a database of thousands of questions. The test is made up of a couple hundred questions, but you have no idea which couple hundred are going to be selected.
Finally, a working
captain convinced me to take a course at Sea
School. They teach you a more focused
scope of material that is geared for the tests that they administer for the Coast Guard. They have a very high success rate with their approach. You also have the opportunity to ask questions and learn from other class mate's experience. This was the best way to go from my experience.
I am glad that I studied the Wing book in addition to taking the
classes. I learned a lot from both, but the class was the best way to prepare you for, and pass the test.
I also suggest that if you take the OUPV class, take the masters class as soon as possible after it (if you want the masters license), and apply for your
license after you take the masters class. This will save you
money (from having to apply for both licenses seperately) and the OUPV material will be fresh in your mind as you study the masters material.
It also depends on how you learn. Some people can absorb material from reading better than classroom learning and vise versa. I do know captains that studied from
books, made their own flash cards for test prep, and passed the test fine.