Kalman's original paper is quite theoretical and somewhat irrelevant to most modern implementations of the algorithm.
As I mentioned earlier, Kalman filters, by their nature, are implicitly matrix, or more properly, state-space, problems.
Another book, Eli Brookner's "Tracking and Kalman Filtering Made Easy," shows that the Kalman filter, when simplified is actually functionally equivalent to various other filters such as the alpha-beta filter.
The alpha-beta filter paradigm is probably the only half-way simple description of the Kalman filter.
Don't know if you're done all the websearches, but there are a number of websites as well as Matlab code floating around.
TTFN