local bookMod = RegisterMod("MyMod",1)
local bookItem = Isaac.GetItemIdByName("Mod")

local useItemCount=0
local evaluateCacheCount=0;

function bookMod:useItem(CollectibleType, RNG)
    local player = Isaac.GetPlayer(0)
    player:AddCacheFlags(CacheFlag.CACHE_FIREDELAY)
    player:EvaluateItems()
    useItemCount=useItemCount+1
    return true
end

function bookMod:evaluateCache(player, cacheFlag)
    evaluateCacheCount = evaluateCacheCount +1
    if cacheFlag == CacheFlag.CACHE_FIREDELAY and player:HasCollectible(bookItem) then
            player.MaxFireDelay = player.MaxFireDelay - 3;
  end
end

function bookMod:postUpdate()
    Isaac.RenderText("useItemCount :"..useItemCount, 50, 30, 255, 255, 255, 255)
    Isaac.RenderText("evaluateCacheCount : "..evaluateCacheCount, 50, 15, 255, 255, 255, 255)
end

bookMod:AddCallback(ModCallbacks.MC_POST_UPDATE, bookMod.postUpdate)
bookMod:AddCallback(ModCallbacks.MC_USE_ITEM, bookMod.useItem, bookItem)
bookMod:AddCallback(ModCallbacks.MC_EVALUATE_CACHE, bookMod.evaluateCache)