Heating is not necessary.
From my understanding it facilitates a process known as decraboxylization in which the THC changes to a form that is more readily absorbed by the GI tract, the onset is faster and the effects more pronounced when you cook it in fatty foods (cannabinoids are soluble in oils) such as firecrackers with peanut butter.
You can get effects from eating it raw but it will take more bud. You need not make anything extravagent like cookies or brownies, Leary biscuits and firecrackers are easy and effective.
Leary biscuits involve taking a ritz cracker with a slice of cheese and half gram or so of good quality cannabis on top microwaved...I have never tried microwaving before and would recommend you lower the power setting so it doesn't get too hot.
Firecrackers you take a two ritz crackers and cover them generously in peanut better, put broken reefer and then put them together to form a sort of peanut-butter cracker sandwhich then place in the over at 275F for about 20 minutes.