It depends on how many elements/states of the system are put into the modeling, what the preliminary information about the mutual influence of the states between the elements andt their states are to be considered, what the outer conditions influence the evolution of the states of single elements, etc. For generalities, any book on random (stochastic) processes might be useful, however from the question a suggestion follows, that probably some theory of semi-Markov processes were useful, if the evolution is non-Markovian and the number of states is not to high. A pretty wide fashion of such processes with applications is given in the monograph
Semi-Markov Processes: Applications in System Reliability and Maintenance, by F. Grabski: