I'm studying chemical engineering for more than two years and what I can tell you is that there is not really a lot of "good" books you may read as an introduction.
You have to understand that Chemical Engineering contains both "Chemical" and "Engineering". The first one refers to chemistry whereas the second refers to the way to make something. A chemical engineer who works at Metalor (which makes precious metal bars amidst other things) really has not the same problems as another one working at Air Liquide (which produce liquid gas).
Now if you are looking for what we call the basics, any chemical engineer must be good at, fluid mechanics, thermodynamics and kinetics, mathematics and informatics are a good start.
- Fluid mechanics because in any plant, whatever you produce, you need to be able to size pipes, reactors, etc. It's also a must if you encounter a two-phase flow;
- Thermodynamics because when you are sizing somethings you must ensure safety and security so you need to know what properties the molecules involved in your plant have. Kinetics because this is important to know the rate of a reaction and a lof other stuff related to catalysts etc.;
- Mathematics because you can't do the first three without it;
- Informatics because this is pretty hard to perform all the correlations and models by hand when sizing equipment and knowing how to use the common software (Aspen, Matlab) plus having some skills in coding a few lines in either Fortran/C/C++/Python is always a must. Especially if your company does not have the budget to pay the licences and Excel is limited in many ways;
- Finally, mathematics and informatics are a strong requirement to design process and safety control loops efficiently and test them with data from the process before implementation.
If you speak French, the book "Le génie chimique à l'usage des chimistes" by Joseph Lieto gives a pretty good overview about Chemical Engineering. How to make a balance (of mass or energy or momentum), basic operation units (distillation and crystallisation), mass and heat transfer, thermodynamics, kinetics and process control.
The best reference I have for chemical engineering is the McGraw-Hill Chemical Engineering Series which contains more than you should know as a student. After you will need to get strong knowledge in many areas of chemistry (electrochemistry is sometimes a big plus) because as an engineer and a chemist especially if you are looking for sizing operation, you need to think about details (Production practices, HSE, Quality), which are not in the books, unfortunately.