Does anyone know about any good and easy interoductory books which contins information about martingales, sotchastic integration and Lévy-processes?
I have tried reading: http://www.cambridge.org/us/academic/subjects/statistics-probability/probability-theory-and-stochastic-processes/levy-processes-and-stochastic-calculus-2nd-edition and it is very hard, I am not really able to get much out of it. Do you know about any lower level texts you can reccomend please?, which contains stochastic calculus and the theory about Lévy processes?
I would like it to introduce stochastic calculus from scratch, where the only prerequisites are real analysis and measure theory.
It depends a little bit on your interests, but as you might know, stochastic processes and Itô-calculus is excessively used in quantitative finance. I can recommend some books which really explain the basics of stochastic integration and stochastic differential equations. However, these books have a (strong) focus towards financial applications.
If you want more 'difficult' books then I would suggest:
If you are really not interested in any financial applications at all, then I would recommend 'Introduction to Stochastic Integration' by K. L. Chung and R.J. Williams.