Here is a
free book with a few algorithms, grouped in topics:
Chapter 0: Prologue
Chapter 1: Algorithms with numbers
Chapter 2: Divide-and-conquer algorithms
Chapter 3: Decompositions of graphs
Chapter 4: Paths in graphs
Chapter 5: Greedy algorithms
Chapter 6: Dynamic programming
Chapter 7: Linear programming
Chapter 8: NP-complete problems
Chapter 9: Coping with NP-completeness
Chapter 10: Quantum algorithms
The individual chapters and the book as a whole are available for download.
I have not looked into this book that much, I can't say if it's good or substantial. I think it's best to have several sources for algorithms because that way you usually also get several different examples which might help a lot.