Ok that's fiberglass bat insulation, approximately R-3 per inch so a total of R-9. You can easily add more insulation on top of that - either buy more rolls of bat insulation (UNFACED - which means no paper layer on either side) - or you could blow in cellulose insulation (buy at Home Depot and get the blower rental for free.
Downside to cellulose is you need a body suit, respirator mask (not just a simple dust mask) and two people (one to feed the machine, one to blow it in the attic). Upside is it's 3.70 per inch so adding 15 inches would get you R-55, plus your existing R-9 is R-64.
Fiberglass bats, they're easier to install (roll em out, each layer criss crossing the previous) - but they usually come 3.5 inches thick - so you'll need to add 5 layers, which adds up pretty fast cost wise.
WELL worth it for the energy savings - but for a newbie, I'm gonna say spend more $ and get the bat insulation that's easier to roll out. And wear gloves, long sleeved clothing, and heavy socks and tape your pants to your socks and your shirt sleeves to your gloves...