Hello friend,
Regarding uniqueness - after a good amount of thinking and asking for suggestions from at least 5 to 10 people in the organization - some of whom have joined recently - your design will surely be unique.
Look at the HR manual from a user's perspective - what an employee would like to have as a ready reference, what matters to him, what is relevant to him in performing his role, what information will strengthen his/her work - prepare a list of contents and discuss with colleagues from HR, other departments, and also some seniors to finalize.
Any manual generally evolves with time, so do not attempt to be a perfectionist - as soon as you reach an adequate level - just release it. After about a year, you may like to revise/improve.
Generally, the manual will contain - Company Mission, Vision, Brief History, HR Policies and Service Conditions, and Rules, etc.
Regards,
Nishikant