There are plethora of books, notes & websites available to acquaint you with theoretical chemistry and Density functional theory.
As mentioned in the above answer "Introduction to Computational Chemistry" by Frank Jensen + "Essentials of Computational Chemistry: Theories and Models" Book by Christopher J. Cramer, are good start for beginners.
Now, I know going through book by book is most of the time a length process but fruitful, however, there are series of Lecture notes on Theoretical Chemistry & Electronic Structure Methods by Dr. Sherrill which you can access free of cost:
--> Now, coming to your specific need to learn DFT, ok Density Functional Theory is a mathematical tool that is being used in chemistry for performing theoretical calculation. For you to understand DFT you first need to clear your basics and get a grip on Matrix Algebra, Dirac Notations, Calculus & Differential Equations because you gonna need a lot, from the sources mentioned above. When you reach this end there is a simple startup book for DFT for chemists its:
"A Chemist's Guide to Density Functional Theory" Book by Max C. Holthausen and Wolfram Koch.
A good place to start it's a book "Introduction to Computational Chemistry" by Frank Jensen. But If you want more practical knowledge of how to actually perform the calculations, you should look for the software manual. I'm using Orca for instance, and they have a great manual, which is very practical and useful for beginners. Also, if you want any more tips, you can contact me directly via direct message.
There are plethora of books, notes & websites available to acquaint you with theoretical chemistry and Density functional theory.
As mentioned in the above answer "Introduction to Computational Chemistry" by Frank Jensen + "Essentials of Computational Chemistry: Theories and Models" Book by Christopher J. Cramer, are good start for beginners.
Now, I know going through book by book is most of the time a length process but fruitful, however, there are series of Lecture notes on Theoretical Chemistry & Electronic Structure Methods by Dr. Sherrill which you can access free of cost:
--> Now, coming to your specific need to learn DFT, ok Density Functional Theory is a mathematical tool that is being used in chemistry for performing theoretical calculation. For you to understand DFT you first need to clear your basics and get a grip on Matrix Algebra, Dirac Notations, Calculus & Differential Equations because you gonna need a lot, from the sources mentioned above. When you reach this end there is a simple startup book for DFT for chemists its:
"A Chemist's Guide to Density Functional Theory" Book by Max C. Holthausen and Wolfram Koch.
It gives: A basic understanding of how the concepts and models underlying the various manifestations of DFT are built, and an essential knowledge of what can be expected from DFT calculations and how to achieve the most appropriate results.
1) Computational Chemistry -Introduction to the Theory and Applications of Molecular and Quantum Mechanics - Errol Lewars-KLUWER Academic Publishers - Provides a general overview and also specific technical approaches in Comp Chem. including DFT
2) Review Article by Frank Neese(ORCA): Prediction of molecular properties and molecular spectroscopy with density functional theory: From fundamental theory to exchange-coupling. Com. Chemistry Reviews 253(2009) 526-563
I find very useful for the very beginning discussion, the book from Weitao Yang and Robert Parr "Density Functional Theory of atoms and molecules" there you can find a valuable standard for foundations on the theory as discussion of Hohenberg and Kohn theorems and references to original work of Thomas Fermi and others who developed the very early stages of the exchange-correlation functionals. As matter of introduction in notation and mathematical backgroud in our lab we use the classical book of Szabo and Ostlund "Modern Quantum Chemistry Introduction to Advanced Electronic Structure Theory", "Molecular electronic structure theory" from Trygve Helgaker, et. al. and in a bachelors level the books of "Physical Chemistry" of McQuarrie and "Quantum Chemistry" from Ira N. Levine as well as "Molecular Quantum Mechanics" due to Peter Atkins. The sources for information are available on the internet as well as many of the further readings in the books, I hope this may help, best wishes.