I'm trying to link C++ code to the bamtools library. My directory structure is:

myproject/
  Makefile
  lib/
    bamtools-master/
  include/
  src/bam_example.cpp

The lib/bamtools-master/ file is the contents of https://github.com/pezmaster31/bamtools/archive/master.zip

My code is:

include "api/BamMultiReader.h"
#include "api/BamWriter.h"
#include <iostream>
#include <stdlib.h>
using namespace std;
using namespace BamTools;
BamMultiReader reader;

int main(int argc, char* argv[]) {
  cerr << "Test";
}

The Makefile is:

bam_example:
    g++ -I ./lib/bamtools-master/include/ -L ./lib/bamtools-master/lib/ -o bam_example src/bam_example.cpp -lz -lbamtools

clean:
    rm bam_example

When I compile I get:

$ make
g++ -I ./lib/bamtools-master/include/ -L ./lib/bamtools-master/lib/ -o bam_example src/bam_example.cpp -lz -lbamtools
$ ./bam_example 
./bam_example: error while loading shared libraries: libbamtools.so.2.3.0: cannot open shared object file: No such file or directory

What went wrong here? What is the correct way to link to bamtools library?

What is wrong with this example?