🚀 go-pugleaf

Hi,
I am programming a freeware(open-source) chess program and am looking for
experience or advice in some points.
I am using the bitboard representation : a square is represented by a 64-bit
integer containing information about that square : piece if any, EnPassant
flag,...
For Searching (the best move) I am using some variant of alphabeta called
MTDF, and using transposition tables to store some calculated positions
evaluations to be used in the next iteration.
For the evaluation function am using an (elementary) evaluation   based on
material balance and some consideration about development , pawn structures
and king protection : and this is my problem : this evaluation is very
elementary and making the program playing really bad.

Am looking for considerations I may include in my evaluation function.
What is the vealuation function used in today chess prog (gnuchess for
example). What Am I missing ? any help is very appreciated (articles, web
refernces, source code).
Is there some consideration for the size of the opening book (am using a
little book : 5 openings) ? Is this really important ?
Any help is much appreciated.
Best regards