I have already have read the book MongoDB: The Definitive Guide by Kristina Chodorow and Michael Dirolf . It doesn't cover much on the PHP, but its a good book to learn about MongoDB and how it works in Depth. Once I saw the book, MongoDB and PHP by Steve Francia I was planning to buy it, and the time I got a chance to signup for the blogger review program by O'Reilly Media. Its a small book of 60 pages, but a good one. I will rate 7.5 / 10 , a good read for PHP Developers . If you wondered why the 2.5 is missing read on

I have little experience playing with MongoDB and Lithium framework . I loved to give an 8 / 10 for the book really . But the reason why I didn't gave is as its a small book with 61 pages, its really a good way to include installation of MongoDb in atleast one Operating System ( Ubuntu preferred ) . As its not a big pain to install MongoDb in ubuntu its really a good thing :-) . The author Steve has been working with open sky and now with 10gen, and has good experience with MongoDB and PHP . He has presented it nicely, though there are some places need some more clarifications for people new to MongoDB. Even I say its a 60 page book, you cannot just read it in a 3 Hours if you really start playing with it and understanding each and everything .

Some questions I felt in reading page 26 is "If you want to retrieve only the slice itself and not the entire document, you can come pretty close by retrieving the _id and the slice" with the example

print_r($addresses->findone(
    array( 'first_name' => 'Peter', 'last_name' => 'Parker'),
    array('_id' => 1, 'superpowers' => array('$slice' => 2)))
);

The above will give you

Array
(
    [_id] => MongoId Object
        (
            [$id] => 4f2e1b9caa6a477739000000
        )

    [superpowers] => Array
        (
            [0] => agility
            [1] => stamina
        )
)

The above was the only example, but I was thinking something more . What will happen when _id is set to 0 like

print_r($addresses->findone(
    array( 'first_name' => 'Peter', 'last_name' => 'Parker'),
    array('_id' => 0, 'superpowers' => array('$slice' => 2)))
);

it returns

Array
(
    [address] => 175 Fifth Ave
    [city] => New York
    [first_name] => Peter
    [last_name] => Parker
    [state] => NY
    [superpowers] => Array
        (
            [0] => agility
            [1] => stamina
        )
    [zip] => 10010
)

and what about _id when removed like

print_r($addresses->findone(
    array( 'first_name' => 'Peter', 'last_name' => 'Parker'),
    array('superpowers' => array('$slice' => 2)))
);

will return

Array
(
    [_id] => MongoId Object
        (
            [$id] => 4f2e1b9caa6a477739000000
        )

    [address] => 175 Fifth Ave
    [city] => New York
    [first_name] => Peter
    [last_name] => Parker
    [state] => NY
    [superpowers] => Array
        (
            [0] => agility
            [1] => stamina
        )

    [zip] => 10010
)

Somethings like this are left to user to think why its so ? Some example like 'Clark Kent' was never created, nor I remember whether he mentios to create new ones. It would have been a good idea to mention to insert new ones as the book teaches how to do it. The other one which confuses me about Indexing , ie whether I want to run the method ensureindex each and every time or only once Eg :

$db->numbers->ensureindex(array( 'num' => 1 ));

But once you finish reading the book carefully, you will definitely can use MongoDB for your next project . He covers different types of ODM for MongoDB. For further information look into the product page at http://shop.oreilly.com/product/0636920022381.do