I always recommend 'Grow your own vegetables' by Joy Larkcom, about £7 on Amazon. It is a bible but written in an easy-to-understand way. Has planting calendars, info on how to prepare your plot, all of that. Also loads of interesting veg varieties and info on how to grow them.
My advice: start small (ie cover most of the plot with something that will keep the weeds out) and only grow a few things depending on how much time you have and how far away from home/work it is. You will start off with good intentions and ideas but trying to tackle a large plot is what puts people off.
Also only grow what you really like and what you can't buy cheaply in the supermarket. I would never bother with carrots, for example, as they are so cheap to buy. More interesting varieties of potatoes, however, are good bet and nothing beats the taste of freshly dug potatoes, steamed and served with a little butter and salt.
My old allotment neighbour used to say how do you eat an elephant ? In small bites. Just take it step by step and whack some seed or bought veg plants as you go along. I've been given purple sprouting broccoli and sprout plants that have just gone in.
Last night I sowed Florence Fennel which is better sown after the longest day so it doesn't bolt. Also lettuce, beetroot, pak choi, mange tout and radish. A new family started last night and did look quite daunted but a couple of hours later a little clear patch emerged. I've got loads of raspberries and strawberries to offer people so hopefully people on your site will be able to give you bits to get you started.
Maybe buy a few herb plants and stick them in (or ask friends if they are able to split any of theirs). Take your camera up and take regular pictures which are great motivators when the going gets a bit tough as some days it will seem. And leave a space for somewhere to sit and look over your hard work. I got a bench in Wilkos for £12.50 which is useful for sitting and dumping your tools on.
I've just got a plot too, but its very overgrown, but luckily its got a pear tree and a plum tree on it that are fruiting very well. So we've decided to use the next few months to clear the plot and make the beds and pathways, maybe grow some winter crops but generally get everything ready for next spring. And we shall always have our fruit to harvest in the autumn.